I do custom paint for people. Mostly friends and such. I use top of the line Urethane Paint, etc. For a good standard paint job with no body prep other than scuffing/sanding you can expect at a minimum 2K. Now if your existing paint can't support being coated over then the whole thing needs to be taken to metal $$$$. It also depends on the current mil thickness of the existing paint.
I generally like to do 2-3 coats of primer and 3 coats of color followed by 5 coats of clear. Or you may want a candy that will add 1-3 coats. With Urethane that will last almost forever, at least till your grandkids get it. If someone wants more clear, I ablige at cost.
Another consideration is sanding/buffing. I get some people that don't mind a bit of "orange peel" so they don't want to pay for the 10-20hrs of wetsanding. I can get a final flash damn good without having to sand but most people like it because it makes a good paint job look like a show paint job. You can also do this yourself. It is time consuming but simple.