… revenue Google has earned from Android since its launch in 2008: $550 million … [Google's] mobile revenue in general, which is on a $2.5 billion annual pace driven mostly by mobile searches on iOS devices and in-app advertising … Android was a defensive move on Google’s part, and one that wasn’t primarily motivated by desire for revenue or profit. … Android represents mobile competition

Quoted from the article, that pretty much sums it up.