They have to give most of that to the credit card companies. I am not sure how much of the 2.75% they get to keep but I would guess less then half, maybe even only a quarter?
They have at least 500 employees -- figure $100k/ea loaded cost, only possible since I think a lot of those employees are not engineers. That's all of it right there.
They really need to be in the 50b/yr range to be doing well. OTOH, they will probably get there in a year or two, and I don't see their costs going up much.