Rear Door replacement

Hi, community.

So my camper was hit from behind and It needs a rear door replacement. I am not convinced with the estimate from the shop repair. They are charging painting and fiberglass. Why are they are charging that?
Does not the new back door replacement comes already finished? I mean painted and matching my model. In this case, would be 320 boondock-2021.

Does anyone have changed a hatch or back door and got charged for painting?
I have attached a partial picture of the estimate.