I believe so. However, even if it's not I don't see any other platform allowing you to use their service and sidestep platform fees. Someone mentioned above that there might be limitations for the number of keys, but I'm not aware.
They're demonstrably not. I'd advise you to read up on the concept of a monopoly.
> They made 17 Billion in rev last year, so nearly 25 Billion went to game makers / publishers. This is 2-3x what spotify paid to artists in the same year.
And? I don't understand why you're just comparing two values in absolute values. You're talking as if Valve is giving away money.