To elaborate: They have released a "compendium", which gives you some goodies related to the upcoming "The International 4"-Tournament. It allows you to participate in a fantasy league and make predictions on the winners. A quarter of the money you spend on it goes to the prizepool of the tournament, which started out at 1,6 million $ and has reached 2,200,000 in less than 8 hours it's been available, with these hours being mostly night/morning in Europe and America. Last year they got to $2,874,407 in several months, which was already considered huge.
That means Valve has made already sold $2.4 million worth of these things, and are likely to make a lot more. I really like this business model working out.