We know that Apple has tons of apps, music, and movies on iTunes and we know that there are tons of downloads each month. Apple keeps a chunk of the money for each item sold on the iTunes network to help pay the bills and stock its coffers with loot for things like building spaceship campuses. I've never really stopped to think what it costs Apple to run the iTunes store, support the bandwidth needed for all those downloads, and other costs.
What we know of the iTunes store is that it is packed with 15 billion songs, had has 130 million book downloads, 14 billion apps downloads, and has paid out $2.5 billion to devs. There are 225 million accounts, 425,000 apps, 90,000 iPad apps and 100,000 game and entertainment titles available. Asymco took the data I just mentioned and cobbled it together with data that was already available and used that info to come up with an idea of what Apple pays to run iTunes.
The number works out to something in the range of $113 million monthly assuming the store runs at break even. The $113 million monthly number assumes a total income of $313 million monthly income from the store. The numbers, if correct, suggest that Apple pays $1.3 billion per year to run iTunes. We could also safely assume that there is enough money left each month (and probably lots of it) to expand the capacity of the store.