I don't see how the idea that Steam should get a share approaching 30% is any less repugnant than that. Visa gets less than 4%, and they are the ones that are really processing the charge. Valve eats that much, and whatever they get paid over that is simply for their role in facilitating the transaction

If any of these three parties declined to provide their own involvement, a sale does not happen. So all of them are reasonably entitled to a share. But not necessarily a whole third.

I agree that Half-Life developers should not be the ones getting the majority of the sticker price of CounterStrike, insofar as those people are disparate parties and the popularity of CounterStrike drives sales of HL and even surpasses Half-Life in popularity. But it is impossible to deny that CS does not have a game to sell at all without HL.

They did sell "CS-Only" discs without the ability to play Half-Life in single-player mode, didn't they? And, Valve still got a cut? (What's that? They never did? Hmm...)

Edit: There is obviously some risk for Valve, too. Maybe more than Visa in the long run, but I think they will pass on the risk to those who they pay, just like Visa. They do get to hold the money, and they can decide who gets paid.