It has more to do with how much work the bumper will need than what the shop WANTS to charge. If it needs to be painted, it obviously has been hit by something and requires some bodywork. Is it scratched, gouged, chipped? These are things that need to be stated in order to give an accurate estimate. True it would cost about 200-250 to JUST paint a bumper. But if it needs 2-3 hours of bodywork its going to cost more. I think if you want an estimate on something you need to include a picture or its not even worth asking unless it is to JUST paint a panel or part.