What Michael said, and then the condition comes into it. There will be a difference between one the is in say "mint condition" and one that has been "rode hard and put up wet".
Next is the weight of the green tip limbsm and the condition. Ultra light or ultra high weights are hard to come by. Limbs from 50 to 60# are about the average.
Past that there are a few other considerations such as if it was signed by Fred Bear, Frank Scott, or some others. A good signature can really push the price up. I had one at one time that had gold clamps. It was a very uncommon one that you just don't see every day.
I just sold a signed one to a guy with 55# limbs, and traded an unsigned one with 70# limbs to another guy.
One thing you can do is go to e8ay and search for one in the completed items section to see what they have sold for.
Are they worth it as shooters? Go see what a new Bear custom takedown is going for nowadays.
Hope this helps a bit, although I did not give you an exact answer.
I guess, bottem line is, "what is it worth to you"?