All joking aside, and I am giving them the benefit of doubt, if it was as simple as putting in a bigger battery and changing nothing else about the controller, surely they would have done it? Price alone can't be the reason they chose to skip adding a big battery since they can simply charge more. Perhaps the size of the battery itself is not the reason but there is one.Those people will tell you that "you don't know anything about batteries"
Thinking it is simply out of greed is easy but the reasonable side of me says: "...just because I make something does not mean people will be forced to buy it..." so I think there is definitely a reason outside of "greed". The battery life is not something they are trying to hide or are they?