I think that like anything else that's equipment-specific and labor intensive, you gets what you pays for. A 1st class powder job requires real skills, takes several steps, uses some specialized equipment, and it helps if the person who's doing it has a real sense of pride in the finished product. So...better to pay more (especially with good references) and be happy with the results.
Otherwise, your bike frame may wind up with a finish like patio furniture, which is a pretty common powder coating mainstay. Don't get me wrong- I like my patio furniture and it's comfy and all, but I wouldn't want to ride it.