You do realize that the 30% that Google takes from Android Developers from App sales doesn't go to Google right?
But even if they don't, Google is still serving ads to Android users AFAIK. While browsing on exactly that topic (pondering whether to flip the profit bit on the Android entry), I ran across an estimate of $1 billion: http://www.forbes.com/sites/ericsavitz/2011/02/08/googles-an... This made the decision an easy one.