It depends on a *lot* of factors. Most shops won't be able to quote a price unless they see the piece in person. The type of metal involved is also a big factor... brass is supposedly the easiest to work with so it's cheaper than Aluminum (probably the hardest). In addition, the quality of the metal is important... if you bring in something that has the surface smoothness of wrought-iron, it would take a *lot* of time to smooth it out enough to get a truly glossy finish. However, a well polished or at least 'smooth' piece of metal is a lot easier to polish, and is therefore cheaper.
My shroud was pretty much 'brushed' aluminum so it was pretty expensive. Some of the other pieces he's going to do are of much better 'start' quality, so they will be cheaper. Although, the first set of stuff I brought in received an estimate of about $450 to chrome, so... I'm exploring other options =p. Some of the stuff really won't have to be done, inner, non-visible components and such. I'm *really* hoping to bring everything down to $200'ish.
The guy is the best in Dallas though... I could probably get it done cheaper elsewhere, but this guy is crazy skilled. I was referenced by a low-rider guy that works at one of my clients companies. He did all the work on his car... take a look =p.
Before:
After:
Of course, the whole car was restored, so the second picture is showing a lot more than just the quality of the chrome, but... there it is. He's good ^_^.