It is misleading. It is 30% of the entire revenue of the game. And it is objective whether Valve deserves 30% of that revenue. It’s also true that games aren’t locked to the Steam platform and can absolutely make money outside of Valve’s influence. History has shown though that it is less profitable then being inside the Steam ecosystem.

The efficiency is doing it so effectively that on an open platform competitors can create there own store, pay for AAA games to appear on their store, take the smallest of pay cuts, pass it on to the consumer, and still have customers prefer to pay more to be in the Steam ecosystem. I’m against monopolies but Valve’s is absolutely efficient.