Asked before - I don't think ever answered.....

[H Gilmer3]

If I register on Steam, even though I spent my money here and I will be giving Steam no money, will Ageod have to give Steam any money for that? I'd like to register on Steam and play and comment and help the game out, but I also don't want Steam to get your money.

But, I guess if others buy and like the game based on my comments, it in the long run helps Ageod.....

Hmmm.

[bob.]

Nope, Steam won't receive any money specifically from you registering your key.

I don't know how the deals with Valve are exactly, but one thing is for certain: individual key registrations are not part of it

[H Gilmer3]

Cool. I'll register then.

[bob.]

I actually got curious myself and I found this in the Steam Greenlight notes:

If my game is accepted through Steam Greenlight, can I give my previous customers keys for the Steam version?
Once your game is accepted for distribution on Steam, we will give you as many keys for your game as you want at no cost.

I would assume that this is the same for games that did not go through Greenlight. Valve in general seems to be very generous about things like this.
If you think about it, it is a win-win situation: the developer can give out Steam keys and Valve gets additional Steam users. Since the servers are already standing, the additional cost for them is negligible.

[Pocus]

Exactly, as you say bob.