Dealer quoted $700 to run wire for backup cam, Need Advise

$125.00 an hour is not out of line for shop time. I would guess that the shop has no idea what they would eventually get into, so they bid the time high. Pulling wires when you have no idea what is behind each wall or dropping the ceiling can turn into a big clustercluck in no time. From their point of view they would much rather bid the job based on six hours and get it done in three than bid three and have it run into six.