Since Ludeon apparently doesn't monitor their support forums I e-mailed them. I will post the answer here to help anybody else wondering.
"Valve doesn't get any money.
I don't know exactly why they let us sell Steam keys like this. I think it's mainly because 97% of the sales are still on Steam, and they see Steam key sales as a way to get new people to start using Steam (so they can buy Steam games later). It also reduces the incentive for developers to move off Steam."
It makes sense for Valve to do this. 97% still buys via Steam though, that's awful. People should try to buy directly from the developers themselves - they make the game so they should get the money. Valve usually takes a very unfair cut.
"Valve doesn't get any money.
I don't know exactly why they let us sell Steam keys like this. I think it's mainly because 97% of the sales are still on Steam, and they see Steam key sales as a way to get new people to start using Steam (so they can buy Steam games later). It also reduces the incentive for developers to move off Steam."
It makes sense for Valve to do this. 97% still buys via Steam though, that's awful. People should try to buy directly from the developers themselves - they make the game so they should get the money. Valve usually takes a very unfair cut.