Zedex on 22 June 2011
Guys this isn't even counting steam sales! :P
"During the Games For Change event going on New York City today, Valve’s Gabe Newell mentioned that Portal 2 has sold 3 million copies since April 18.
Newell didn’t mention any platform specifics, as it was, according to Joystiq, a comment made in more of a passing manner, but it’s likely he was implying the total unit sales on all playforms.
Otherwise, that would be an amazing feat, indeed.
Joystiq also noted the first Portal moved 4 million units by the time Portal 2 launched, and that figure does not take Steam sales into consideration."
http://www.vg247.com/2011/06/22/valve-portal-2-has-sold-3-million-copies-since-launch/
