I bought a 94 JD 855 4x4, hydro trans, with 70A front end loader, 2 rear blades, and 60 inch mower with about 1100 hours on it. Very good condition. Got it 2 years ago for $10,000.
...but seriously, check tractorhouse.com and machinefinder.com. It will give you a very good idea of what they are selling for, or at least advertised for.