Grigby, I built and flew a two place Challenger from a kit many years ago and the good news is that although the owner and founder of the company died fairly recently the plane is still in production so parts and support are still readily available. The reason you are seeing prices all over the place is due to many factors. Age & condition of the airframe, type of powerplant and number of hours on the engine, damage history, extras like the optional fiberglass nose cone, Lexan doors,cabin heat, tundra tires, wheel pants, carbon fiber or wood prop, condition of the paint, instruments, radio, will it need recovering any time soon, is it N numbered? Is it the long wing or clipped wing version? Probably 95% of all Challenger 11 aircraft came equipped with the Rotax 503 dual carb
dual ignition engine which Rotax no longer makes although parts are still readily available. But an out of production engine does affect the price. There have been a number of improvements over the years like a stronger and taller vertical stabilizer, stronger lift strut attach points for increased payload especially with amphibious floats, easier entry due to cabin frame rails situated lower, improved redrive able to swing a longer diameter prop, and the list goes on and on. Also, with the new Light Sport category and certified aircraft available for use as student trainers it makes the older category aircraft somewhat obsolete which of course drives the price down. If I were you I would contact the Challenger dealer closest to you and ask him to do an appraisal for you. You may be able to get a rough appraisal over the phone with a Facetime call on your phone with the dealer able to see the condition of the plane and tell you what to point the camera at. In your description of the aircraft every little detail is significant to someone looking to buy a plane like that. Is it a true project aircraft, or is it partially disassembled for an in depth inspection and the engine removed due to reaching TBO and now needing a fresh overhaul. Many, many variables to consider so prices as you say will be "all over the place." Hope this helps.