I think the even bigger advantage Valve has is the business model.

I don’t know how much the Deck costs Valve to manufacture. And yes, it’s pretty easy to run non-Steam games. But the bottom line is that the Deck does not have to be a profit center for Valve, it just has to drive more sales on Steam without losing too much money. Logitech, Lenovo, Asus, etc have to make money off of the hardware.