Just the boots?? Your front CV's presumably have 140k miles on them. Have new or rebuilt OEM axles put on. 650 for materials and labor to install just the boots sees quite HIGH and you could still be faced with CV issues in the near future.
These refer to the axles that run to the drive wheels, common in front wheel drive as it allows the wheels to follow suspension and steering. The cv joints allow the wheels to move while the axle remains perpendicular to the transmission. The rubber shrouds over the CV joints are the boots. In RWD driveshaft we call them u-joints. FWD we call them CV joints. Not much difference, except FWD are expected to run at tighter angle than driveshafts normally move
I just paid $450 for a new front axle after discovering a large amount of grease leaking out of the inner boot. The boot had been replaced 5 years ago, but now the joint was finally failing. I think your quote for just the boots is a little too high.