1: Higher auction prices mean higher final values
2: Sellers generally do not care about "maximizing" to the last penny; but in aggregate, a 3 dollar increase on winning bids equates to large income increases from final valuations (why ebay changed rules on shipping and handling a couple months ago)
3: Buyers feeling "safe and secure" bid highest (if they know there is risk they set their max bid accordingly)
4: On thousands of transaction per day, a 10 percent increase in final valuations means lots of money
5. By sticking the seller with the costs of a reckless buyer, and skewing polices and feedback toward the seller, ebay increases income and avoids all risk through creating a situation where buyers risk is so small they can bid blindly and KNOW they can always count on ebay/paypal
6 NO other commerce site provides such a reckless environment for "buyers"
7. Only a fool plays this game as a seller when they know how it works