Did you remove bearings when you powder coated your wheels? I am about to powder coat mine as well('85 R80). Is there anything I need to be cautious when prepping for powder coating?
You should remove the bearings, and you dont want to powder coat the part where the disc brakes are, since it can result in giving a strange rotation to the whole wheel. That mistake was done on this bike, but even than it is easy to remove it with something sharp enough.
The cost to build it depends of many things. The biggest problem is to find a bike in great condition. Once you have a good stock model its all about your imagination, time and money :)