App store apps give Apple lock-in to the iOS platform. Even if an app is available for Android, I would need to buy it again, which means I have friction to switch platforms. If everything is a web app, I can switch at will.
There are two big obstacles I see for web apps to take over:
* Poor interoperability between apps (solved by WebIntents)
* Monetization (though services like GitHub and Flickr do this well, and there are providers like http://chargify.com/ to make it easy for developers)
It's not the app revenue, it's the locked content stream. Open web apps would be able to sell content directly, as they never signed the app store contract. Long term Apple's growth model requires content sales. Hardware sales only grew 7% over last year if I remember their filing correctly.
Actually I think you're about a factor 10 off there, hardware sales FY11 was $99bn, compared to $57bn in FY10, which is a growth year over year of about 72%, while content saw growth of about 28% from $4.9bn to $6.3bn. As for total impact on revenue, hardware sales made up 91% of total revenue in '11, compared to 88% in '10.
Of course, I'm open to other interpretations.
[1] http://www.wired.com/gadgetlab/2011/12/ios-revenues-vs-andro...
[2] http://www.apple.com/pr/library/2011/10/18Apple-Reports-Four...
[3] http://files.shareholder.com/downloads/AAPL/1856667914x0xS11...
[4] http://www.pcworld.com/article/226531/apples_popular_apps_no...
[5] http://www.quirksmode.org/mobile/