I'd speculate you might be wrong with that last statement. A long rifle by a well-respected maker, in high condition compared to most, with a direct connection to some historical event or figure might reach into the $100,000 plus range like some of the high end European arms. Look at the Atchison Hawken that just sold for $109,250. That certainly shows over $100,000 is possible with the right rifle and history. Atchison himself isn't even a well-known or highly influential figure.
All that said, the most expensive long rifle I've seen personally was $40,000 as the price including the buyer's premium.