diff --git a/src/components/bom/BomPanel.tsx b/src/components/bom/BomPanel.tsx
index 67ad905..69cbce1 100644
--- a/src/components/bom/BomPanel.tsx
+++ b/src/components/bom/BomPanel.tsx
@@ -2,10 +2,17 @@ import { useMemo } from 'react'
 import { computeBom } from '../../domain/bom'
 import { useProjectStore } from '../../state/projectStore'
 
+function formatCost(value: number): string {
+  return `$${value.toFixed(2)}`
+}
+
 export default function BomPanel() {
   const project = useProjectStore((s) => s.project)
   const bom = useMemo(() => computeBom(project), [project])
 
+  const hasMissingCost =
+    bom.devices.some((line) => line.devicesMissingCost > 0) || bom.cables.some((line) => line.connectionsMissingCost > 0)
+
   return (
     <div className="space-y-4 p-3">
       <section>
@@ -14,6 +21,13 @@ export default function BomPanel() {
           <p className="text-xs italic text-slate-400">No devices on the canvas yet.</p>
         ) : (
           <table className="w-full text-xs">
+            <thead>
+              <tr className="text-left text-[10px] uppercase tracking-wide text-slate-400">
+                <th className="pb-1 font-medium">Device</th>
+                <th className="pb-1 text-right font-medium">Count</th>
+                <th className="pb-1 text-right font-medium">Cost</th>
+              </tr>
+            </thead>
             <tbody>
               {bom.devices.map((line) => (
                 <tr key={line.key} className="border-b border-slate-100 last:border-0">
@@ -26,6 +40,14 @@ export default function BomPanel() {
                     )}
                   </td>
                   <td className="py-1 text-right font-medium text-slate-600">×{line.count}</td>
+                  <td className="py-1 text-right text-slate-600">
+                    {line.totalCost > 0 ? formatCost(line.totalCost) : '—'}
+                    {line.devicesMissingCost > 0 && (
+                      <span className="ml-1 text-[10px] text-amber-500" title="Some devices are missing a cost">
+                        ({line.devicesMissingCost} unset)
+                      </span>
+                    )}
+                  </td>
                 </tr>
               ))}
             </tbody>
@@ -44,6 +66,7 @@ export default function BomPanel() {
                 <th className="pb-1 font-medium">Cable</th>
                 <th className="pb-1 text-right font-medium">Count</th>
                 <th className="pb-1 text-right font-medium">Total length</th>
+                <th className="pb-1 text-right font-medium">Cost</th>
               </tr>
             </thead>
             <tbody>
@@ -59,12 +82,34 @@ export default function BomPanel() {
                       </span>
                     )}
                   </td>
+                  <td className="py-1 text-right text-slate-600">
+                    {line.totalCost > 0 ? formatCost(line.totalCost) : '—'}
+                    {line.connectionsMissingCost > 0 && (
+                      <span className="ml-1 text-[10px] text-amber-500" title="Some cables are missing a computable cost">
+                        ({line.connectionsMissingCost} unset)
+                      </span>
+                    )}
+                  </td>
                 </tr>
               ))}
             </tbody>
           </table>
         )}
       </section>
+
+      {(bom.devices.length > 0 || bom.cables.length > 0) && (
+        <section className="border-t border-slate-200 pt-2">
+          <div className="flex items-center justify-between text-xs">
+            <span className="font-semibold uppercase tracking-wide text-slate-500">Grand total</span>
+            <span className="font-semibold text-slate-700">{formatCost(bom.grandTotalCost)}</span>
+          </div>
+          {hasMissingCost && (
+            <p className="mt-0.5 text-[10px] text-amber-500">
+              Some items are missing a cost and are excluded from this total.
+            </p>
+          )}
+        </section>
+      )}
     </div>
   )
 }
diff --git a/src/components/inspector/ConnectionInspector.tsx b/src/components/inspector/ConnectionInspector.tsx
index d1b66da..32aa33f 100644
--- a/src/components/inspector/ConnectionInspector.tsx
+++ b/src/components/inspector/ConnectionInspector.tsx
@@ -20,6 +20,8 @@ export default function ConnectionInspector({ connectionId }: { connectionId: st
     return sourcePortType && targetPortType ? cableTypesForConnection(project, sourcePortType, targetPortType) : []
   }, [project, sourcePort, targetPort])
 
+  const cableCostPerUnit = availableCableTypes.find((ct) => ct.id === connection?.cableTypeId)?.costPerUnit
+
   if (!connection || !sourceDevice || !targetDevice || !sourcePort || !targetPort) return null
 
   return (
@@ -76,6 +78,33 @@ export default function ConnectionInspector({ connectionId }: { connectionId: st
         </div>
       </label>
 
+      <label className="block text-xs font-medium text-slate-600">
+        Cost override
+        <div className="mt-1 flex items-center gap-2">
+          <span className="text-xs text-slate-500">$</span>
+          <input
+            type="number"
+            min={0}
+            step={0.01}
+            value={connection.cost ?? ''}
+            onChange={(e) =>
+              updateConnection(connection.id, {
+                cost: e.target.value === '' ? undefined : Number(e.target.value),
+              })
+            }
+            className="w-full rounded border border-slate-300 px-2 py-1 text-sm"
+            placeholder={
+              cableCostPerUnit !== undefined && connection.distance
+                ? `computed: $${(cableCostPerUnit * connection.distance).toFixed(2)}`
+                : 'e.g. 24.99'
+            }
+          />
+        </div>
+        <p className="mt-1 text-[10px] text-slate-400">
+          Overrides the cable type's per-unit cost for this run specifically. Leave blank to use cost/unit × distance.
+        </p>
+      </label>
+
       <label className="block text-xs font-medium text-slate-600">
         Label
         <input
diff --git a/src/components/inspector/DeviceInspector.tsx b/src/components/inspector/DeviceInspector.tsx
index a3968ab..5b64943 100644
--- a/src/components/inspector/DeviceInspector.tsx
+++ b/src/components/inspector/DeviceInspector.tsx
@@ -49,7 +49,7 @@ export default function DeviceInspector({ deviceId }: { deviceId: string }) {
             className="mt-1 w-full rounded border border-slate-300 px-2 py-1 text-sm"
           />
         </label>
-        <label className="col-span-2 text-xs font-medium text-slate-600">
+        <label className="text-xs font-medium text-slate-600">
           Model
           <input
             value={device.model ?? ''}
@@ -57,6 +57,23 @@ export default function DeviceInspector({ deviceId }: { deviceId: string }) {
             className="mt-1 w-full rounded border border-slate-300 px-2 py-1 text-sm"
           />
         </label>
+        <label className="text-xs font-medium text-slate-600">
+          Cost
+          <div className="mt-1 flex items-center gap-1">
+            <span className="text-xs text-slate-500">$</span>
+            <input
+              type="number"
+              min={0}
+              step={0.01}
+              value={device.cost ?? ''}
+              onChange={(e) =>
+                updateDevice(device.id, { cost: e.target.value === '' ? undefined : Number(e.target.value) })
+              }
+              className="w-full rounded border border-slate-300 px-2 py-1 text-sm"
+              placeholder="e.g. 249.00"
+            />
+          </div>
+        </label>
         <label className="col-span-2 text-xs font-medium text-slate-600">
           Notes
           <textarea
diff --git a/src/components/palette/CableTypeManager.tsx b/src/components/palette/CableTypeManager.tsx
index 43babd2..11875ff 100644
--- a/src/components/palette/CableTypeManager.tsx
+++ b/src/components/palette/CableTypeManager.tsx
@@ -21,7 +21,13 @@ function CableTypeForm({
   initial?: CableType
   portTypes: PortType[]
   onCancel: () => void
-  onSave: (fields: { name: string; endAPortTypeId: string; endBPortTypeId: string; unit: CableType['unit'] }) => void
+  onSave: (fields: {
+    name: string
+    endAPortTypeId: string
+    endBPortTypeId: string
+    unit: CableType['unit']
+    costPerUnit?: number
+  }) => void
 }) {
   const initialEndA = initial ? portTypes.find((pt) => pt.family === initial.family) : undefined
   const initialEndB = initial ? portTypes.find((pt) => pt.family === (initial.family2 ?? initial.family)) : undefined
@@ -30,12 +36,19 @@ function CableTypeForm({
   const [endAPortTypeId, setEndAPortTypeId] = useState(initialEndA?.id ?? portTypes[0]?.id ?? '')
   const [endBPortTypeId, setEndBPortTypeId] = useState(initialEndB?.id ?? portTypes[0]?.id ?? '')
   const [unit, setUnit] = useState<CableType['unit']>(initial?.unit ?? 'ft')
+  const [costPerUnit, setCostPerUnit] = useState(initial?.costPerUnit?.toString() ?? '')
 
   const isAdapter = endAPortTypeId !== endBPortTypeId
 
   const handleSave = () => {
     if (!name.trim() || !endAPortTypeId || !endBPortTypeId) return
-    onSave({ name: name.trim(), endAPortTypeId, endBPortTypeId, unit })
+    onSave({
+      name: name.trim(),
+      endAPortTypeId,
+      endBPortTypeId,
+      unit,
+      costPerUnit: costPerUnit.trim() === '' ? undefined : Number(costPerUnit),
+    })
   }
 
   return (
@@ -87,6 +100,19 @@ function CableTypeForm({
           ? 'Different connector on each end — this becomes an adapter cable, letting those two port types wire together even if nothing else declares them compatible.'
           : 'Same connector on each end — a regular cable for that connector type.'}
       </p>
+      <div className="flex items-center gap-1.5">
+        <span className="shrink-0 text-[10px] font-medium text-slate-500">Suggested cost/{unit}</span>
+        <span className="text-xs text-slate-400">$</span>
+        <input
+          type="number"
+          min={0}
+          step={0.01}
+          value={costPerUnit}
+          onChange={(e) => setCostPerUnit(e.target.value)}
+          placeholder="optional"
+          className="w-0 min-w-0 flex-1 rounded border border-slate-300 px-1.5 py-1 text-xs"
+        />
+      </div>
       <div className="flex justify-end gap-2">
         <button onClick={onCancel} className="text-[11px] text-slate-500">
           Cancel
@@ -126,7 +152,13 @@ export default function CableTypesPanel() {
     return a === b ? a : `${a} ↔ ${b}`
   }
 
-  const handleCreate = (fields: { name: string; endAPortTypeId: string; endBPortTypeId: string; unit: CableType['unit'] }) => {
+  const handleCreate = (fields: {
+    name: string
+    endAPortTypeId: string
+    endBPortTypeId: string
+    unit: CableType['unit']
+    costPerUnit?: number
+  }) => {
     const endA = portTypes.find((pt) => pt.id === fields.endAPortTypeId)
     const endB = portTypes.find((pt) => pt.id === fields.endBPortTypeId)
     if (!endA || !endB) return
@@ -135,13 +167,20 @@ export default function CableTypesPanel() {
       family: endA.family,
       family2: endA.family === endB.family ? undefined : endB.family,
       unit: fields.unit,
+      costPerUnit: fields.costPerUnit,
     })
     setCreating(false)
   }
 
   const handleUpdate = (
     id: string,
-    fields: { name: string; endAPortTypeId: string; endBPortTypeId: string; unit: CableType['unit'] },
+    fields: {
+      name: string
+      endAPortTypeId: string
+      endBPortTypeId: string
+      unit: CableType['unit']
+      costPerUnit?: number
+    },
   ) => {
     const endA = portTypes.find((pt) => pt.id === fields.endAPortTypeId)
     const endB = portTypes.find((pt) => pt.id === fields.endBPortTypeId)
@@ -151,6 +190,7 @@ export default function CableTypesPanel() {
       family: endA.family,
       family2: endA.family === endB.family ? undefined : endB.family,
       unit: fields.unit,
+      costPerUnit: fields.costPerUnit,
     })
     setEditingId(null)
   }
@@ -197,6 +237,7 @@ export default function CableTypesPanel() {
                     <div className="font-medium text-slate-700">{ct.name}</div>
                     <div className="truncate text-[10px] text-slate-400">
                       {describeEnds(ct)} · {ct.unit}
+                      {typeof ct.costPerUnit === 'number' && ` · $${ct.costPerUnit.toFixed(2)}/${ct.unit}`}
                     </div>
                   </div>
                   <button
diff --git a/src/components/palette/DeviceTemplateEditor.tsx b/src/components/palette/DeviceTemplateEditor.tsx
index 68e3e75..1247272 100644
--- a/src/components/palette/DeviceTemplateEditor.tsx
+++ b/src/components/palette/DeviceTemplateEditor.tsx
@@ -45,6 +45,7 @@ export default function DeviceTemplateEditor({
   const [category, setCategory] = useState<string>(template?.category ?? 'other')
   const [manufacturer, setManufacturer] = useState(template?.manufacturer ?? '')
   const [model, setModel] = useState(template?.model ?? '')
+  const [cost, setCost] = useState(template?.cost?.toString() ?? '')
   const [ports, setPorts] = useState<DraftPort[]>(
     () =>
       template?.ports.map((p) => ({ key: p.id, name: p.name, direction: p.direction, portTypeId: p.portTypeId })) ?? [
@@ -120,6 +121,7 @@ export default function DeviceTemplateEditor({
       category,
       manufacturer: manufacturer.trim() || undefined,
       model: model.trim() || undefined,
+      cost: cost.trim() === '' ? undefined : Number(cost),
       ports: ports.map((p) => ({ id: p.key, name: p.name.trim() || 'Port', direction: p.direction, portTypeId: p.portTypeId })),
     }
     if (template) {
@@ -156,7 +158,7 @@ export default function DeviceTemplateEditor({
               className="mt-1 w-full rounded border border-slate-300 px-2 py-1 text-sm"
             />
           </label>
-          <label className="col-span-2 text-xs font-medium text-slate-600">
+          <label className="text-xs font-medium text-slate-600">
             Model
             <input
               value={model}
@@ -164,6 +166,21 @@ export default function DeviceTemplateEditor({
               className="mt-1 w-full rounded border border-slate-300 px-2 py-1 text-sm"
             />
           </label>
+          <label className="text-xs font-medium text-slate-600">
+            Suggested cost
+            <div className="mt-1 flex items-center gap-1">
+              <span className="text-xs text-slate-500">$</span>
+              <input
+                type="number"
+                min={0}
+                step={0.01}
+                value={cost}
+                onChange={(e) => setCost(e.target.value)}
+                className="w-full rounded border border-slate-300 px-2 py-1 text-sm"
+                placeholder="e.g. 249.00"
+              />
+            </div>
+          </label>
         </div>
 
         <div>
diff --git a/src/domain/bom.ts b/src/domain/bom.ts
index 426ecc9..c80f0e1 100644
--- a/src/domain/bom.ts
+++ b/src/domain/bom.ts
@@ -1,5 +1,5 @@
 import { allCableTypes } from './project'
-import type { Device, Project } from './types'
+import type { CableType, Connection, Device, Project } from './types'
 
 export interface BomCableLine {
   cableTypeId: string
@@ -9,6 +9,11 @@ export interface BomCableLine {
   /** Sum of user-entered distances; connections with no distance are excluded. */
   totalLength: number
   connectionsMissingLength: number
+  /** Sum of each connection's cost (its own override, or `costPerUnit *
+   *  distance` when both are known); connections with no computable cost are
+   *  excluded rather than counted as zero. */
+  totalCost: number
+  connectionsMissingCost: number
 }
 
 export interface BomDeviceLine {
@@ -18,17 +23,49 @@ export interface BomDeviceLine {
   manufacturer?: string
   model?: string
   count: number
+  /** Sum of `device.cost` across instances; devices with no cost set are
+   *  excluded rather than counted as zero. */
+  totalCost: number
+  devicesMissingCost: number
 }
 
 export interface Bom {
   cables: BomCableLine[]
   devices: BomDeviceLine[]
+  /** Sum of all cable line totals (missing-cost connections already excluded). */
+  totalCableCost: number
+  /** Sum of all device line totals (missing-cost devices already excluded). */
+  totalDeviceCost: number
+  /** `totalCableCost + totalDeviceCost`. Missing costs are excluded, not
+   *  treated as zero, so this is a lower bound whenever anything is flagged
+   *  as missing below. */
+  grandTotalCost: number
 }
 
 function deviceGroupKey(device: Device): string {
   return device.templateId ?? `${device.category}:${device.manufacturer ?? ''}:${device.model ?? device.name}`
 }
 
+/** A connection's cost for BOM purposes: its own override if set, else
+ *  `costPerUnit * distance` if both the cable type's rate and the
+ *  connection's distance are known. Undefined means "not computable" —
+ *  callers must exclude it from totals rather than treating it as zero. */
+function connectionCost(connection: Connection, cableType: CableType | undefined): number | undefined {
+  if (typeof connection.cost === 'number' && !Number.isNaN(connection.cost)) {
+    return connection.cost
+  }
+  if (
+    cableType &&
+    typeof cableType.costPerUnit === 'number' &&
+    !Number.isNaN(cableType.costPerUnit) &&
+    typeof connection.distance === 'number' &&
+    !Number.isNaN(connection.distance)
+  ) {
+    return cableType.costPerUnit * connection.distance
+  }
+  return undefined
+}
+
 export function computeBom(project: Project): Bom {
   const cableTypes = new Map(allCableTypes(project).map((ct) => [ct.id, ct]))
 
@@ -44,6 +81,8 @@ export function computeBom(project: Project): Bom {
       count: 0,
       totalLength: 0,
       connectionsMissingLength: 0,
+      totalCost: 0,
+      connectionsMissingCost: 0,
     }
     existing.count += 1
     if (typeof connection.distance === 'number' && !Number.isNaN(connection.distance)) {
@@ -51,6 +90,12 @@ export function computeBom(project: Project): Bom {
     } else {
       existing.connectionsMissingLength += 1
     }
+    const cost = connectionCost(connection, cableType)
+    if (cost !== undefined) {
+      existing.totalCost += cost
+    } else {
+      existing.connectionsMissingCost += 1
+    }
     cableLines.set(connection.cableTypeId, existing)
   }
 
@@ -64,13 +109,28 @@ export function computeBom(project: Project): Bom {
       manufacturer: device.manufacturer,
       model: device.model,
       count: 0,
+      totalCost: 0,
+      devicesMissingCost: 0,
     }
     existing.count += 1
+    if (typeof device.cost === 'number' && !Number.isNaN(device.cost)) {
+      existing.totalCost += device.cost
+    } else {
+      existing.devicesMissingCost += 1
+    }
     deviceLines.set(key, existing)
   }
 
+  const cables = [...cableLines.values()].sort((a, b) => a.cableTypeName.localeCompare(b.cableTypeName))
+  const devices = [...deviceLines.values()].sort((a, b) => a.name.localeCompare(b.name))
+  const totalCableCost = cables.reduce((sum, line) => sum + line.totalCost, 0)
+  const totalDeviceCost = devices.reduce((sum, line) => sum + line.totalCost, 0)
+
   return {
-    cables: [...cableLines.values()].sort((a, b) => a.cableTypeName.localeCompare(b.cableTypeName)),
-    devices: [...deviceLines.values()].sort((a, b) => a.name.localeCompare(b.name)),
+    cables,
+    devices,
+    totalCableCost,
+    totalDeviceCost,
+    grandTotalCost: totalCableCost + totalDeviceCost,
   }
 }
diff --git a/src/domain/project.ts b/src/domain/project.ts
index 97990ce..a03dfd3 100644
--- a/src/domain/project.ts
+++ b/src/domain/project.ts
@@ -172,6 +172,7 @@ export function createDeviceFromTemplate(
     manufacturer: template.manufacturer,
     model: template.model,
     ports: template.ports.map((port) => ({ ...port, id: uuid() })),
+    cost: template.cost,
     position,
   }
 }
diff --git a/src/domain/types.ts b/src/domain/types.ts
index 4445ee5..73af5aa 100644
--- a/src/domain/types.ts
+++ b/src/domain/types.ts
@@ -63,6 +63,9 @@ export interface DeviceTemplate {
   manufacturer?: string
   model?: string
   ports: Port[]
+  /** Suggested default cost, copied onto each placed Device at creation time
+   *  (same as ports) and independently editable per instance afterward. */
+  cost?: number
   builtIn?: boolean
 }
 
@@ -77,6 +80,10 @@ export interface Device {
   model?: string
   notes?: string
   ports: Port[]
+  /** Copied from the template's suggested cost when placed (like ports),
+   *  then independently editable — editing an instance never mutates the
+   *  shared template. */
+  cost?: number
   position: { x: number; y: number }
 }
 
@@ -95,6 +102,9 @@ export interface CableType {
    *  not just where this particular cable is actually used). */
   family2?: string
   unit: 'ft' | 'm'
+  /** Suggested default cost per unit length (in `unit`). Each Connection can
+   *  override the computed cost for its specific run (`Connection.cost`),
+   *  which always wins — public catalog prices drift and vary by vendor. */
   costPerUnit?: number
   custom?: boolean
 }
@@ -110,6 +120,11 @@ export interface Connection {
   /** User-entered run length, in the CableType's unit. Optional because
    *  real-world layout isn't modeled (no floor plan / scale). */
   distance?: number
+  /** Override for this specific run's total cost — takes precedence over
+   *  computing from the CableType's `costPerUnit * distance`, since a
+   *  diagram-level price should always win over the library's suggested
+   *  default. */
+  cost?: number
   label?: string
   notes?: string
 }
diff --git a/src/state/projectStore.ts b/src/state/projectStore.ts
index 1cd812b..8842ea9 100644
--- a/src/state/projectStore.ts
+++ b/src/state/projectStore.ts
@@ -28,7 +28,10 @@ interface ProjectStoreState {
 
   addDeviceFromTemplate: (templateId: string, position: { x: number; y: number }) => void
   updateDevicePosition: (id: string, position: { x: number; y: number }) => void
-  updateDevice: (id: string, patch: Partial<Pick<Device, 'name' | 'category' | 'manufacturer' | 'model' | 'notes'>>) => void
+  updateDevice: (
+    id: string,
+    patch: Partial<Pick<Device, 'name' | 'category' | 'manufacturer' | 'model' | 'notes' | 'cost'>>,
+  ) => void
   removeDevice: (id: string) => void
 
   /** Returns the new port's id, so the caller can move keyboard focus to it. */
@@ -46,7 +49,10 @@ interface ProjectStoreState {
     targetPortId: string
     cableTypeId: string
   }) => boolean
-  updateConnection: (id: string, patch: Partial<Pick<Connection, 'cableTypeId' | 'distance' | 'label' | 'notes'>>) => void
+  updateConnection: (
+    id: string,
+    patch: Partial<Pick<Connection, 'cableTypeId' | 'distance' | 'cost' | 'label' | 'notes'>>,
+  ) => void
   removeConnection: (id: string) => void
 
   addCustomDeviceTemplate: (template: Omit<DeviceTemplate, 'id' | 'builtIn'>) => void