They are, but not really that much. Automakers frequently run harnesses with unused wires for lower trims because the expense to inventory multiple parts is mo

They are, but not really that much. Automakers frequently run harnesses with unused wires for lower trims because the expense to inventory multiple parts is more than the wire costs. So it isn't so expensive that they don't waste some wire. On many models there's already a harness run to the front of the roof for other reasons, (garage door opener, compass, safety systems, dome lights, map lights, visor lights, mirror dimmer, microphone) so the labor and assembly costs are mostly already happening anyway. We're talking tens of pennies or single digit dollars of additional cost in material at most. If we pick a popular vehicle with this feature, a 2010 F150, there's a 16 pin connector there, with 12 wires populated. 2 are for the camera. Does it cost more than running 10 wires there? Yes. Was it so much that Ford didn't actually ship the car that way? No. https://www.f150forum.com/attachments/f38/470443d1489862009-2010-f150-video-cap-mirror-16-pin-plug-2010-rear-view_1.jpg https://www.f150forum.com/attachments/f38/470443d1489862009-...