When I check the auctions, I see H&H large bores gong for upwards of 40,000 pounds only when it was one of Hollands personal guns - even shotguns.

I see most rifles going for around 20,000 or less, soemtimes much less.

Of course, we don't know what the final 'deal' was - perhaps an offer of $15,000 purchased them, we'll never know.

A gun is worth exactly you can get for it.