That's just PC sales. In April this year XBox 360 sales reached 12M and PS3 sales were 1.5M.
That aside, the real money is in merchandising and tie-ups
Minecraft also makes more on merchandising sales than software sales.
Half the under-13s in the country have or will have a Minecraft t-shirt, lunchbox and/or action figure. The game revenue is a small part of it. If you have kids you probably know the mindshare this game has. It's bigger than any video game I remember.
It'd be interesting to see Microsoft make Minecraft a free addition to every licensed copy of Windows.