Fergus,
I've had similar experiences. There's really nothing to understand, other than anyone can rent table space, put a PHD after their name if they wish, and act like a total jerk anywhere, anytime.
In this case, he was probably telling a lie to pump up his ego...at $9,700 he deserves to be the last owner. Bet if you see him at the next show, you'll see the same gun on his table. You were too polite in thanking him...but you made the right decision to walk away...I would have run!

"I hate rude behavior in a man. I won't tolerate it" - Capt. Woodrow Call