Well tens of millions of dollars in annual revenue usually gets you about 500 million. They would really want it bad to pay more than 2 billion. They might have to layoff some people at Redmond to pay for it.
Also, they are swallowing some pride here. At last Build they said it is not in their interest to develop for iPhone or Android. They were pushing for Android and iPhone devs to port their application to Windows phone. I guess they are finally accepting the facts and are done dreaming and hoping.