Businesses have used shadier techniques to increase sales before... increasing prices to trick people, tricking people every other product is bad for you, shrinking the product.
I think, the best example I can use here is the Cadbury company. People were starting to suspect that the Cadbury easter eggs were getting smaller every year, but since they would only get bought once a year no one could really be sure. They started accusing Cadbury of shrinking the eggs but keeping the prices the same, but Cadbury said that it only looks smaller because you're getting bigger/older, and people fell for it.
A few years ago, someone finally compared it, and saw that the previous egg was smaller than the current egg, and yet the prices had stayed the same.
http://videosift.com/video/EASTER-SC...-are-Shrinking
http://articles.businessinsider.com/...m-simplicity/2
Point is, businesses do this all the time, and customers don't realize it if the shift is subtle enough. It's hardly a crazy conspiracy. There is no doubt in my mind DLC will get abused, because it'll be easier to do it than Easter eggs, because it's much harder to proportionally compare a game against another game.