30% is and isn’t a lot when you consider everything it entitles you to do as a developer, including high-speed download servers, community tools, advertising, SteamWorks platform etc.
The work valve is doing in development of Proton isn’t an occasional trinket, it’s an ongoing and important project which is helping to defeat the real monopoly, Microsoft.
Also, I’m a patient gamer, Steam sales are frequent enough that I have always paid the best price.