Looks to me like the Sigma is a Black Friday / Cyber Monday promotion that B&H is putting on. It\'s probably a loss leader for them. Seems each retailer will have their own promotions during this period. You can\'t expect price matching for these type items. You just buy, or snooze and lose.
I just bought this from B&H as it was another Black Friday deal. Only going to last until December 3rd. 50% off. Did not find that price anywhere else.