This subject is a real can of paint worms. Prices vary greatly, because the work can vary greatly.
Removing things not getting painted (bumpers, chrome etc.) will help with price, as will masking off for them.
If you don't mind Bondo, that will help. Prep hours and sheet metal fabrication cost money.
If you want all the gaps and lines nice, and all fiberglass or metal (no bondo), that's gonna cost ya.
Probably the cheapest quote you will get is if they literally just need to apply paint. Everything's been prepped for them, and/ or you don't care if the rest is not perfect, paint away.
If they do a wet sand/polish etc after, it might save you dough to do that for them as well. Its not hard, just takes time.