Do you have a .edu email address?
Try the Ultimate Steal if you are affiliated with a uni/college.
I got Win 7 Pro for $30 earlier in the year, its at $60-$70 now though.
the cheapest ur really going to find is 99 bucks at newegg. try making a thread on the FS forums. I havent seen alot of people selling copies tho. or what till Christmas sales popup and see if it goes on sale.