When you're locking a rate through advance payment, you're hedging yourself against any future price increase. If the hotel suddently fills up with guests, you'd bet the rate will increase sharply : if that's what you expect, you're better off doing advance purchase. In this economy, however, with low occupancy, droves of customers have become uncommon, so you often get no price increase between the "advance purchase" offer and the "please come to our hotel last-minute because we're empty" offer. I understand your frustration, but advance purchase doesn't mean "best price guarantee" it just means you'll pay this price (which you must have found interesting, since you booked it) even if the price fluctuates, in either direction, before you check-in. The fact the rate decrease happened just after you booked must be infuriating, and I feel your pain.