Google made the same argument in this case, but Epic responded by saying that impairing the competition is sufficient to describe the behavior as unlawful. Like Google, Valve control the vast majority of the market, charge a fee that is way above the cost of service, and have rules that make the competitors less appealing. Like this one:

In response to one inquiry from a game publisher, in another example, Valve explained: “We basically see any selling of the game on PC, Steam key or not, as a part of the same shared PC market- so even if you weren’t using Steam keys, we’d just choose to stop selling a game if it was always running discounts of 75% off on one store but 50% off on ours. . . .”

(source)

You mean like Play Store?

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