It's worth as much as anyone is willing to pay for it. For the most part, they don't shoot bad as far as accuracy is concerned, all have a 1:48 twist. The locks and triggers are usually quite sloppy unless someone has taken the time to rebuild and tune them - weak and broken main springs are also common and CVA no longer supports these guns. They also have ignition and cleaning issues with flash channel. It's hard for me to see from the picture but the drum relies on the lock plate for support to prevent it from eventually being broken off by the impact of the hammer. In the pic, it appears that the drum on this one is not in contact with the lock plate - yes, it's correctable but a time consuming job to do correctly if you want it to look nice - yes this is a serious safety issue. The stock design and complete lack of balance cause these to be very user un-friendly to many people, make sure you can hold it or you'll only be shooting it off a stick/bench.
I started in black powder many moons ago with this same gun but mine was a flintlock and came as a kit (it was cheap and money was tight). The flintlocks share the same problems as above with the addition of several others, there's lots of reasons I got rid of it long ago.
