Looking at my confirmations, the most I have paid is $64 (all in, with taxes) for a 3+ star. As paytonc said above, there is free night/weekend parking in CC. You can then take the hotel shuttle to DCA or a cab for a few bucks. Another option is to park at an outlying metro station (also free night/weekend parking) and ride into the hotel.

In my cases, I have always stayed in Crystal or Pentagon City to be on the metro to go to dinner with friends. I also wanted to be able to check in during the afternoon and get some work done so restricted it to 3* with wi-fi.

There are a few hotels that will show up on on Priceline if you search Arlington area that are off the metro with free parking and an airport shuttle. I think Days Inn, Comfort, and Best Western. Those are even cheaper but wouldn't work for my schedule.

Also check www.ecolonial.com which lists locations and daily rates of some lots around there.

local info
 

Parking in the "economy" lot is $14 per day. Parking in the luxury garage is considerably more. I have parked at the curb in Crystal City and walked to the terminal. It depends on how much luggage and the weather.

On a weekend, I would think several Crystal City hotels would offer "park and fly" rates that would be reasonable. They may not be readily available on the generic hotel websites, so perhaps try calling individual properties and negotiating the rate to include parking. I suspect it simply depends on the weekend and if there are any significant events going on in D.C.