I live in southern Illinois, not exactly a high cost area. I think a full time working painter who can turn out show quality paint jobs should price his work so he makes at least $1,000 a week, after expenses, especially if he is working in his own shop, where he has to come up with the insurance, the tools, the lights, the 15% social security, and deal with the EPA and other government crap.
I'm not full time; I don't do that great of work; I am not that fast, so I don't command that kind of money.
Median family income is around $42,000 a year. Painting cars is not only very highly skilled work, it is hard physical labor.