We know that the App Store is a big deal for Apple -- witness the news earlier this week that customers had spent $1.1 billion at the App Store in the two weeks surrounding Christmas and New Year's. But how big a deal? J.P. Morgan analyst Rod Hall published a memo noting that Apple's share of the revenue (after the 70% payout to developers) was about $6.4 billion for the 2015 calendar year.
AppleInsider, which published the results of Hall's note to investors, notes that while the App Store isn't a huge source of revenue for Apple, it's what keeps people tied to the iOS platform. A healthy App Store means a healthy Apple.