Even the Display could have sustained water damage.
I keep old scrapped systems so I can use their parts for testing other systems....such as verifying if the Display or Keyboard on your laptop are Ok. Unfortunately most places don't have this ability since Apple has the techs return the old damaged parts...so a tech must order the part(s) they know for sure are damaged and see what else may be bad once they have the ability to test the other items. Theoretically the tech should be able to return those parts if they are not needed and the repair is declined, however, they are unable to return the Top Case Assembly housing the battery, keyboard, trackpad, touchbar, and speakers so someone would have to pay for this part if the repair is declined (bet if won't be the AASP as they would go out of business quickly).
With newer Macs this process gets even harder & more complicated.
You should talk with the AASP and find out whether you are liable for those costs if the currently quoted parts are not enough to fix the laptop. I'm sure you will be liable for some labor costs regardless if the Mac is repaired or not just for the tech's time.