Occasionally, I have run across a complete ready to fly .40 size trainer (with radio and engine) for sale used right at $100. Usually the planes this cheap are n need of repairs, and if the radio is useable (on a currently legal frequency, and meets the "narrow band" requirement) the NiCds are usually no good.

RIGHT NOW, I am getting ready (doing repairs and testing) to sell off a USEABLE trainer, complete package deal, and I expect to sell it for about $175. That's about what you should expect to pay for a GOOD, flyable used aircraft with radio and engine, not needing replacement batteries, or repairs for safety... just fuel it and fly.