

Valve doesn’t overcharge me.
They provide an excellent user experience. They have one of the few stores where you can actually get reliable user reviews. Their return policies are generous. I’ve never had any problems with fraud or scams. Their search and recommendation functions are pretty good.
To me, that’s a great deal and they’ve earned every penny of their markup.
“overcharge” is entirely in the eye of the purchaser not the devs. Given the difference in user experience between Steam and any other launcher (sadly even/especially GOG), Steam charges less than I’d be willing to pay.