At one time I was able to buy them for under $15 each. They were cheap scales that done the job. I sold a few sets here on RCTech. I never had complaints that they were bad or didn't work.
http://www.rctech.net/forum/r-c-item...ing-tweak.html
These here would work too as suggested by SWTour. More capacity and a bit cheaper.
http://m.harborfreight.com/1000-gram...ale-60332.html