Pretty much anything that goes on an aircraft you can add a few zeros to the cost. So your $100 wingtip video camera would likely be north of $10k before it was certified. Plus it's unnecessary weight, and if you're going to feed it to the PFD, it'll need to be fully protected for HIRF/Lightning - which also adds cost and weight - often a lot.
Not quite the same as a video camera - FADECs are Level A flight critical hardware. But the electronics in a FADEC box are considerably less sophisticated than the typical laptop that you can pick up for less than $1,000. By the time they are qualified for the aircraft environment, the LRU cost for a FADEC is in the $250k - $500k range.
