To the OP: you think it is expensive to pay $79 to get 35,000 points? That is enough points for one night at a category 7 hotel. Most of us value Marriott points at a penny per point.

Realistically, the DC area is your best bet for getting a cheap room since Marriott has a lot of properties there. The wintertime is low season there since tourism drops off during this part of the year.