Purchasing used games from EB really rips off developers. EB get's all the money and they keep it for themselves. You should really buy new games as that supports the people who made it and then they can make more.
Essentially when you buy a new game, you're sort of paying for that one, but mostly you're paying for them to make the next one.
To the developer, when you buy a used game, it's like piracy, but you gave your to money to EB games instead of keeping it. Literally they see just as much money from someone who bought a used game as from someone who stole it.
Spend the extra 5 bucks, so great companies like Bioware can keep making the games we love to play.