Minecraft is actually extremely profitable, though. It's rumored that Notch already has a personal income in the realm of $100M/year derived from real revenue, not funding. This is very, very different from, say, Snapchat.
From what I can tell they still depend almost entirely on Minecraft, which, if I've followed gaming correctly, has as many registered players as WoW but pay no recurring subscription fee. Rough calculations seem to indicate MS are going to have to double year on year profitability for ~4-5 years to break even.
The interesting aspect of the purchase is the mindshare. I have kids in elementary and middle school and as far as I can tell, all their friends play it. When my kids went as Steve and a pig (from minecraft) for Halloween last year, they were drawing shouts nonstop from all the kids. Most parents had no idea.
How you turn that mindshare into money is math I don't understand.
