I met a guy at work who said he owned a Beretta O/U with a 3 barrel set...20 bore, 375H&H and 470NE.As mentioned they tend not to be favored for dangerous game. An O/U is generally easier to regulate, though.
Said he had paid $54K and that included custom fitting the stock at the factory in Italy.
He could have been completely full of crap, but he had substantial knowledge about all things "double gun".
He said he'd been on several safaris...etc...etc...
I'd like to believe him, but only because I prefer O/U to a SxS.
I don't even know if that combination is possible.