You're thinking of the single player DLC, specifically the "make the ending suck less" expansion*. I'm talking about the multiplayer DLC, all of which was (and was planned to be) free. The aim of the multiplayer game was to give people who'd finished the game a reason not to take it forthwith to GameStop, and thus drive first-party sales. Charging for the DLC would defeat this purpose. If you've not played Mass Effect's multiplayer, I recommend you do. It's very much like Destiny, albeit on smaller maps. Oh, and you get Mass Effect 3 with it. * something Destiny could do with.