Quick and easy answer;
http://shop.ebay.com/?_from=R40&_trk...All-Categories
http://cgi.ebay.com/NEW-T-MAXX-3-3-4...item5195d5c8ad

Everyone and their brother says their used nitro motors "run great!" when they're trying to sell them. It's rarely true.

Everyone's different, but personally I never pay more than 1/2 retail on a used RC item, and I NEVER buy used nitro motors.