You mean the game devs that they take 30% from in a contract the devs agree to in order to list their game on the largest PC gaming store?

Besides that, steam has an incredibly low financial requirement to start selling your games on their platform. $100 usd per game (at least in the US) and you get it back if your game sells enough copies (100 maybe? I forget tbh.) It’s a great platform for indie devs which is why we’ve seen indie PC gaming boom so much in the past decade or so especially.