Well, IF it's real the price wouldn't be all that off, if you compare the guns
here. The lock on your gun looks like a former flint lock with the piston seat screwed into the side plate with horizontal firing hole, what might indicate against a modern kit gun. But there are so many condition questions on old guns that it's hard to tell the difference from a $300 wall hanger to a $2000 candidate for original rifle shooters.