500 5.56 cleaned brass is priced at $54.00 (all Lake City from what I've seen), packed in an ammo can with free shipping.
Range brass is cheaper, but with this you know it's once fired.
Also if you go to the auction link you can buy pallets of ammo cans and a truck to haul them home in.

Also by buying directly from the US government you can be sure they will use that money wisely.

http://www.govsurplusstore.com/xcart/Fired-Brass.html
Enjoy,
Ed