We used the ones at Wilderness Lodge a couple months ago. They don't take Disney Dollars, but they have a dollar changer and also have a machine where you can buy single boxes of soap and fabric softener.
Seems like it was $2 to wash and maybe another $2 to dry. There are 6 or 7 washers and a few more dryers.
I always seemed to go during peak times and it was packed. Seems everyone else had the same idea to do laundry during the afternoon thunderstorm! haha