They generally go in the $2k-$2.5k range depending on which version (the "R" is the latest and best, the original was also good but I've heard mixed feelings on the in-between "i" version) and condition. Retail was mostly around $4-$5k again depending on model and a few options. Tube types and used life also are going to be factors of course.
Full disclosure I happen to have one which I absolutely love intensely but it's the "all out version" called the "F1 Special Edition". It comes with the upgraded Caps and Cardas internal wiring, also the later heavy duty transformers and sports a special black and silver/gray factory paint. It's the best sounding (and definitely coolest looking) amp I've ever owned. Ironically I've actually upgraded my system to a mega $$$ pair of tube mono blocks so the Cary has been set aside for now because I just hadn't had the heart to part with it just yet...I had always hoped I'd find someone who would give her the well deserved home she deserves...Hmmm