Ouch. I'd probably sue them in small claims court even if it wasn't worth it, just to stick it to them.
Did they paint all the plastics and the tank?
If everything is painted, the bike has gone down in value as one piece I'd say. I won't buy a custom painted bike, and I'm not alone. There is a stigma about them, whether warranted or not. But how much value is lost depends on what shape the bike was before the paint job. Old RC51 bikes, especially ones that need work can be pretty cheap in some areas, so a paint job isn't going to bottom them out much more.
Also, as seen here, RC51's tend to be worth more in parts than in one piece. So parting out the bike can result in decent money. And painted plastics won't affect what kind of money you can get by too much. The painted plastics can be used by many for track days, at the very least.
You can always buy new OEM plastics if the rest of the bike is nice and worth it to spend that $$. It isn't cheap, but you can sell your painted plastics to recoup some of the money.
Last edited by kwtoxman; 01-18-2013 at 12:33 PM.