Gamespot article reveals Valve's cut with steam sales.

[sales2099]

pezus said:

sales2099 said:
That isn't possible. Valve is loved by all and wouldn't do such a thing!

You mean, they wouldn't take any money? 30% does not sound like a lot to me, since it includes a cost for Valve (running Steam)

Id say thats a rather large cut they are taking. Like bordering on criminal.