http://www.joystiq.com/2011/06/22/newell-portal-2-has-sold-3-million-copies-since-launch/
Speaking at Games For Change in New York City (right now), Valve's Gabe Newell casually noted that Portal 2 has sold 3 million copies since its release on April 18. He didn't specify platforms, as it was an incidental reference and not a press release -- but he's probably referring to all platforms (PC, Mac, Xbox 360, and PS3).
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