A live auction has a middle-man (Auctioneer) acting as liaison between what will eventually be two-four bidders (just natural dwindle of interest). The Auctioneer offers a suggested starting price to hook a starting bid, lowering the suggested until someone agrees. Anyone can start the bidding at any price chosen (Ex: Auctioneer says "starting at $100.00, you can start at $5.00 or $5,000.00). They then suggest consecutively higher bids to trump the previous bid. Bidding ends when the auctioneer accepts no more bids, to which the highest recognized bid is taken - new bids may roll back the accepted time or time may be a static point. The highest recognized bid pays the price that the bidder offered as bid - if a bidder wins the auction by bidding $100.00, they pay $100.00. Should the bidder be unable to pay (generally on site and with cash.) then the next highest bidder is awarded the item at the price that they had offered to pay.
The problem Blizz has created is that they place payment as the secondary bid, but the trump bid pays that secondary bid - therefor any bid above the secondary bid has no risk affiliated - no loss of money is made by bidding, save the amount you bid against. Blizz attempts to reconcile that by adding the 15% tax, but with bots putting things up for such stupid prices (see my above for an example of what I mean). The 15% is the only real loss - there was hardly a bid to trump at all. Therefor, you have a risk-less money dump that has a 15% tax for use, only in the event of winning, which provides you with, in essence, any item you damn well please for a 20% cost (about 20%, given the increase in price to lock the item for your own, compiled into the 15% tax.)
Tell me how this makes sense? I can guarantee you that someone is making money on this concept. One half the botting goes to flipping, the other half goes to selling. Easy Peasy Money.