Dutch consumer foundation sues Sony for overpricing digital PlayStation games
(www.gamedeveloper.com)
Steam doesn't have a monopoly, they have a massive market share that they don't abuse. Even on their own platform (Steam Deck), they went out of their way to allow competition by giving access to desktop mode, and you can add non-Steam games to the Steam app, which means I get all the nice platform features from Steam in my EGS and GOG games (Steam Input, Proton, etc).
There's nothing stopping anyone from switching to a competitor, like EGS, GOG, or any of the publisher-specific platforms. EGS even takes a smaller cut, so they can afford to sell games for less, yet they largely don't. PlayStation and Xbox are completely separate platforms, yet prices are similar to Steam, and usually higher for older games.
Valve doesn't set prices, publishers do. If you don't like prices, complain to the publishers, not Valve.
You really need to qualify your argument here that Valve somehow caused higher prices. In fact, if you look at game prices before Steam and adjust for inflation, games are cheaper now.