Have you ever wondered how much Apple has to shell out year after year just to keep iTunes running? I hadn’t either, until 9to5Mac made some interesting observations regarding the application’s total yearly cost. And, believe it or not, Apple’s popular service is setting them back somewhere in the region of $900 million a year.

With new features recently launched, and others on the way, this figure is expected to soar past the $1 billion mark pretty soon.

The figures, which come from Asymco, state that Apple pays $75 million per month for iTunes. This, multiplied by twelve, gives a staggering yearly cost of $900 million (with all the zeroes, just for effect: $900,000,000).

However, let’s not forget: iTunes is a something of a beast. Aside from the application itself, you’ve also got the iTunes Store (including the App Store, and its sneaky approval process), and the new social network, Ping. It’s so much more than just a glorified media player.

And, all these features must increase iTunes’ monthly cost. It makes sense – more services, more people to pay. I for one am just glad iTunes is free. Though I do wonder exactly how much Apple makes from iTunes, regardless of its cost.