You can only get the special discounted prices when a new model's out and they're selling off the older stock.
However there is this site
โฆษณาของมือสอง ซื้อขายสินค้ามือสอง โทรศัพท์มือถือ รถยนต์ บ้าน มือ2 (all in thai though) where you can get really sweet deals. I've seen 24" Intel iMacs going for half the price of my old 20" G5 iMac!
I'll be picking up the 15" MBP after school starts -- probably the second month after, unless sensibility kicks in and makes me wait till the newer ones come out which either means I get more for the same price or the same for a lower price. Since there are 3.06Ghz BTO iMacs available now, there should be 2.8Ghz standard (3.06Ghz BTO) macbook pros soon.