Not sure where you are located, as shipping could have a large impact.
Anyway, I'm a fan of Brown's Plating in Paducah, Kentucky. They did a rear fender from a BSA 441 Victor which required some body work and welding; it came out looking amazing and I believe that I paid $300 ish (they do have a published price list--web based), plus shipping. The fender was turned around in less than 2 weeks. They have also done Norton foot rests, kicker and numerous BMW parts for me. Their chrome has a slight nickel hue that makes it look a bit like stainless steel, my first love...
Bill.