I'd imagine any actual paradox type or bore rifle in a SxS would be extremely expensive. I'll wait to see what price Beretta sets for their gun (if any) but I'll say that prce on the 689 seems way off (perhaps a Gold Sable?) - I was quoted a price less than half of that.
I like and trust Beretta's guns, and I don't feel the same way about Sabatti. I don't know the group buy price for the Chapuis - but Euroguns lists a 9.3x74 "Progress" for well over $6K. That's far more than the Silver Sable, and I'd rather stake a hunt on the Beretta - though that's mostly because I'm familiar with the 680 series guns.