I'm sure I paid <£100 for a set of four Avus centre caps from TPS. IMO its just not worth the hassle of painting them yourself for that, especially taking them apart and then having nice fresh paint on some parts, but scuffed Audi rings etc etc.
If you're getting wheels refurbed, buy the caps first and then you can make sure the refurber has a reference for the paint finish
The only time I'd ask a pro to do centre caps is if I'm changing from the OE wheel colour, and in that case I'd dismantle them first so they just have to prep and paint.