Here's another resource. Try Vacation Rental By Owner
http://vrbo.comYou can contact the owners through their website and see if you can get a condo at your own rate. Here's what I placed on their comments section:
"One adult non-smoker, looking for studio for this time frame 12-08 thru 12-17. (one weekend)
Want to pay $500. Wifi required. I realize it's below rate - but at least it's rented!
Will pay in advance. Please let me know if interested -- Art"I sent it to about 25 different studios all available during those dates. I've received 3 affirmative responses so far. Two were at Gateway Mountain Lodge which is right at Keystone. I booked it!
It's worth a try to "name your own price!" ... especially if it's before the Christmas holiday.
Good Luck