Found this on housekeeping.com:

Front loading washing machines can hold as much as 18 lbs of clothing. So how many items are in a lb. of clothing? To find out how much your loads weigh, you can weigh yourself holding a load of dirty clothing, and subtract it from your weight without the dirty load. While weight varies with type of material, these are some general guidelines. Twin Sized Quilt-3-5 lbs. Complete Child Outfit-1-3 lbs. Complete Adult Outfit-3-5 lbs.

For 2 weeks of clothes, I spend about $15-$17. Apparently this service is $10 per load, so for me, it would end up costing at least $30 (1 whites, 2 colors loads)