Man, for 40 bucks a wheel go ahead and have them powder coated. Shoot, I really don't think you will find a shop that will prep, paint and supply the materials for 40 bucks a wheel. At least a shop that does good work. I'm sure Maco could do it for less but I seriously doubt that they will prep them good. Heck, I paint my own wheels and would rather pay someone to powder coat them at that price. Materials will be more 100 bucks by the time you buy primer, paint and hardener.
BTW, who did you find that will do them for 40 bucks a wheel? Got a phone number?