Gamefly discounts a selection of used video games, with prices starting at $9.99. Shipping starts at $2.98, but several qualify for free shipping. That puts many at the lowest total prices we could find. Sales tax is added where applicable.
A best bet is the used Call of Duty: Modern Warfare 3 for Xbox 360 for $19.99 with free shipping. That's $11 under last month's mention of a new copy with DLC and $16 under the lowest total price we could find for a new one today.