Yeah it seems like errors are prone to happening in the amazon marketplace. Maybe it has something to do with importing the vendors inventory database into the amazon system or something, I dunno.
It's definitely a gamble to try for it, but it seems like sometimes it really is just a good deal, and other times it's a mistake but you luck out and they don't realize it and ship it anyway for the great price. Other times yet, they ship you the wrong item entirely, which Amazon backs you on for returning, but you have to deal with the seller first, an extra PITA IMO. But most times, it seems, with these marketplace 'deals', the vendor realizes it was a mistake, catches it before shipping, and cancels it, no harm no foul (outside of possible having a pending charge on your card for a few days). That's why they call it a gamble I guess. How good of a deal it is and how much it costs needs to play into it -- how much you want to risk/gamble. It was worth it for the sockets, IMO, even if they did get cancelled.