Not accusing anyone of anything here (We have seen what happens when I get too specific), but sometimes an item is relisted like this for a couple different reasons:
1) The bidder did not pay up and the seller got tired of waiting (usually the seller will wait more than a couple days to relist it)
2) The winning bidder bid high to mess with the seller and then told them that they were not buying it. (This would make sense if the bidder had a grudge against the seller)
3) The winning bid was a shill, meant to either drive up the price or protect the investment. When the winner is the shill for the seller, there is nothing to do but relist it. It also helps that the very same people just saw it sell for $370 and now assume that it is actually worth anywhere near that price and often will be happy that they were able to take it for a mere $300 (when in fact, it is worth about $50).
Of course, if you ask me, I say that the seller is 100% above board. What else would I say?
Bill