I don’t want to start a pit thread right now(maybe later), but a large percentage of shops, especially dealerships, will estimate the largest amount they think you will pay without outright leaving and going someplace else regardless of repairs needed.
Just one of many anecdotal examples:
The Chrysler dealership estimated me around $300 to replace the driver side visor. $160 parts and $140 labor. Sure, it included a garage door opener, and the installation included plugging in a standard power connector and screwing in 2 torx screws. A replacement chipped key with a remote fob was around $150 parts.
I don’t know if any studies have been done, I’d be interested in reading them. In my own personal experience, prices on the same type of service and parts vary as much as 3x-4x across shops, and depend a lot on how the person looks when they bring the car in. IF they look like an easy target, they can wind up with an estimate for things broken that aren’t really.
Car repairs are worse than car sales, because most of the time people can walk away from the sale, but once their car is broken, and they went to the trouble of getting the car to the repair shop, they already feel like they’ve made a commitment and most likely won’t shop around, won’t get a second opinion.
How much a high-end aftermarket part costs should be a reasonable estimate of how much it would cost to get an OEM replacement in this case. Because at the very worst they can just install the aftermarket cruise control and hook it up to the existing buttons. Same thing with power door locks.