So what you're saying is, I need 2 accounts, bid $15 with one and then up myself with the fraudulent account to $500 and get the item for 15?
People actually do this on eBay sometimes
The sale goes to the number 1 bidder at some bid increment higher than the number 2 bidder's maximum bid. The current price shown is that amount, not the number 1 bidder's maximum bid. It implements a modified Vickrey auction using an autobidder.