They're talking about "facilitated by the App Store ecosystem" so it includes everything from online shopping to advertising. 1 billion iPhone users spending/generating on average $1000 on their phones per year? Seems reasonable. I think even if you just consider Amazon, the Amazons of elsewhere, supermarkets etc, Ali, it goes on and on. Their combined revenue from people buying stuff on their iPhones, iPads, Mac apps downloaded through the app store will get you a great length towards $1.3 trillion.

People are not spending $1.3 trillion per year on IAPs, it's not the game whales as the other comment suggests.