I agree with Ken, I bought one of these in a .50 cal new in 1980 (I think) and sold it probably 10 - 12 years ago to a friend for $150.00 but it was by no means in excellent condition. I would expect to pay right around $200 for one in great shape, maybe a little more for the .54 cal. I've seen Hawken's which are a much nicer gun in very good shape sell for $175 - $225 also.
It boils down to what is someone willing to pay for it at the time you want to sell it.
It boils down to what is someone willing to pay for it at the time you want to sell it.