That seems cheap by American standards, I've seen punt guns sell for a lot more than that here just as a collectible curiosity piece. I didn't see the pictures of those guns but maybe they were nothing special. A 7 bore isn't too exciting, I've fired larger shoulder guns, to me a 2 bore is a minimum size to be a true punt gun.

Destry

Out there at the crossroads molding the devil's bullets. - Tom Waits