It's always the same: a question of demand and supply...
...I don't know if there are a lot of collectors for exactly such rifles.
In my opinion, a price more than 3000-4000 bucks would be absolutely exorbitant. It's "only" a 150 years old rifle with nice stock carving and some nice features. Maybe it was a donated prize rifle, but in this case there would be a plate on it. I think it was a show rifle, never really used for shooting at the range.
But there are enough really rich collectors, and when one collector wants to own it real bad, maybe he would pay more.
Biggi.