This may be a YRMV deal, but I found Halo: Combat Evolved Anniversary for $14.71 at my local Sam's Club. I have posted a link from the website for people to see if your store has a copy. Please note the website says the game is $24.xx, but I did buy the game locally for $14.71 this morning.
http://www.samsclub.com/sams/halo-combat-evolved-anniversary-xbox-360/prod5060449.ip?navAction=
http://www.samsclub.com/sams/halo-combat-evolved-anniversary-xbox-360/prod5060449.ip?navAction=