expired BioShock Infinite (Steam) for $10.89
Follow the link to gamefly. Click the BUY button. Type in credit card details or link paypal accounts, and apply the coupon code "GFDSEP20" in the final order confirmation screen.
It's confusing as to why GameFly has developed their cart system in this way, but for some reason you can only apply discounts AFTER you've typed in credit card details or made the paypal billing agreement.