Android Economics | asymco
Strategically, and historically Android was never one thing. P&L considerations were not the only (or even at all) factors in investment for Google. Having a hedge against hegemony of potential rivals, having a means to learn and develop new business and having a role in defining the post-PC computing paradigm are all probably bigger considerations than profitability.
So in terms of returns, Android is sustainable. However, in relative terms the value created leaves much to be desired. Whereas Android generates $1.70/device/year and thus an Android device with a two year life generates about $3.5 to Google over its life, Apple obtained $576.3 for each iOS device it sold in 2011. The economics of Android are nothing like the economics of iOS.