My cable is also frayed. Can I cut the cable & just make door manual?

Door mirrors are not cable operated in most cases that I see, and if they need to be replaced it may mean they need to be painted to match car color. That alone drives the cost way up. Sometimes aftermarket replacement mirrors are available or used from salvage yard if you want to chance that.

Silly question , but if it was 'certified' , are you still under warranty? Have you checked YOUR paperwork , rather than going along with what they are trying to sell you? Sometimes they get paperwork (and computer info) wrong , for $1500.00 , I'd check.