4 Pieces of DLC at $10 each
http://www.gamestop.com/pc/dlc/aliens-colonial-marines-season-pass/107753#productDetails
http://www.greenmangaming.com/s/us/en/pc/games/shooter/aliens-colonial-marines-season-pass/
"Hungry for more Aliens: Colonial Marines? Purchase the Aliens: Colonial Marines Season Pass and get access to four downloadable content packages at a 33% discount! All add-on content packs are scheduled to be released from March through to summer 2013. The Aliens: Colonial Marines Season Pass will give you access to campaign content, additional multiplayer maps, new modes, character customisation and more!
If you purchase this Aliens: Colonial Marines Season Pass, all included content should be downloaded in-game and NOT from Steam, or you will be charged twice. Aliens: Colonial Marines game required (sold separately)."