Any hotel on the strip THAT WEEKEND is going to be pricy. I suggest going to Priceline using the Name your own price feature, select, the Convention Area and bidding $70 a night for a hotel. A few people have had success there.
If you're using priceline make sure to select your star level or you may end up in a pretty shady place. Also what they consider "on the strip" is questionable. Hotwire is someone better, because you atleast pick which hotel you'll be at.
Another option is to get someone who already has a room to call & get 2nd room (they'll be able to duplicate their reservation and keep same rate) then you just call again later and transfer the 2nd room into your name.