The stated reason? Because they can do it more cheaply if they know how much capacity they budget for up-front. It's the same reason plan minutes are so much

The stated reason? Because they can do it more cheaply if they know how much capacity they budget for up-front. It's the same reason plan minutes are so much cheaper than overage minutes. Of course, I can't even imagine how that would account for a factor of ten (the lowest on the list), much less 140.