1) Purchase Portal 2 for PS3 from Amazon for $55 and receive a $20 Amazon
credit
2) Use the code found inside the PS3 game case to activate your free PC copy
through Steam.
3) Trade in your Portal 2 PS3 copy to Amazon for $35 (currently)
$55 gets you $20 + $35 in Amazon credit and a copy of Portal 2 for PC
Link: http://www.amazon.com/Portal-2-Playstation-3/dp/B003O6E3C8/ref=
Notice: The Portal 2 PS3 page currently contradicts itself by saying you get
a $15 credit in one play and a $20 credit in another. Not sure which is
accurate but it was $20 before release.
