So where does one look for such deals?
The deals come from people who are not really knowledgable in selling their equipment, where they would mark prices down mistakenly as a PowerMac G5 when it's a Mac Pro 3,1 or 4,1, but that's pretty pretty rare. Or they sell a 5,1 in distress because of a divorce or a bankruptcy; but professionals out there who do this for a living and buy them up and then refurbish them and sell them @ market price. I tried buying these, but always lose out to those seasoned pros!
Prices do come down, but unlike PCs, Macs hold a slight premium over their pricing and people who are selling these macs know there are people out there who are looking for these macs. I was lucky enough to score on a juiced up dual 4,1 flashed 5,1 for half price of the dual 4,1 base model from the store who decided to cut the price by 50% because of the Mac Pro 7,1. But it was his last one as he is expecting the 6,1 pallet coming from the same companies as they upgrade to the 7,1 as he bought the 4,1 and 5,1 used from them years ago. I tracked his price for over a year and he didn't budge a cent until after the 7,1 announcement. However, he is very rare as most others who are selling the 4,1 and 5,1 are not even considering extreme price cuts. Prices will drop, but they will drop slowly because they know most people can't afford the 7,1, which then makes the 5,1 and 6,1 even more valuable. There are still professionals out there who use the 5,1 and 6,1 and won't upgrade and perhaps need replacement computers when theirs break down. So why cut prices when your choices are either 5,1 or 6,1 when you can't afford the 7,1?!?