Did you seriously ignore the well thought out post of someone who knows how these things work so that you could do some armchair economics 101 speculation about equilibrium pricing?Nintendo develops their own hardware ecosystem which means a lot of fixed costs and risk. So do Microsoft and Sony. Valve builds on the existing PC ecosystem. If anything your question proves my point. They are charging developers the same as Nintendo without creating their own hardware ecosystem.
Also, Nintendo has a monopoly on the Switch store, so them charging 30% shows that this is probably the equilibrium monopoly pricing (they can't raise it any further without hurting demand for their store). So yeah, this comparison doesn't put valve in the best light.
Here's the post again for you.
It's not. I have more experience here than basically anyone on this forum TBH.
I have both worked with Valve/Steam for close to a decade and also spent 5 years running an independent digital store (playism)
Valve offers an absolute great value at their 30% cut because compared to other digital stores it is not a goddamn headache to release a game and
actually has easy to access data and marketing features. Not to mention the fact that you get unlimited keys (within reason) basically for free, which is not the case on any other platform.