That's a very rough guesstimation pulled completely out of my ass without absolutely nothing to back it up. I just thought it sounded nice.
...but it doesn't change the fact that there are companies that give away far, far more and ask for far, far less in comparison to what Apple is demanding without going under. Dropbox and Netflix probably use up at least as much as Apple on bandwidth per month and charge considerably less for their services.
One month of Netflix is $8. I can watch 10 movies during that month. That's about the cost of one or two rentals on iTunes, delivered to me at about the same quality. I pay considerably more for Apple's service. I've had months where I've thrown $40-$50 at them, and only downloaded roughly 3GB of data. Netflix? I eat up that much data watching an hours worth of movie.
...so if giving away even a single app for free nets Apple a huge loss despite making more money elsewhere while using less bandwidth overall, why hasn't Netflix gone under?