$4,000.00 paint job
I think $4000 with rust repair, done at a shop, is low.
I'm getting ready to paint my friends Buick GN. I am not charging labor. Zero rust repair needed.
Materials and supplies alone are looking like $1500-$2000.
Find out what products are being used. A $4000 paint job that only looks good for a year or two isn't a very good deal.