True, my bad -- it isn't from a developer PoV, and if the developer forwards the cut to the consumer, Steam is more expensive. This actually regularly happens.

The article does mention this, and also mentions a platform who don't take a cut, and explains how it is difficult to compete with these.

I'd argue though that if you self host instead of outsource (to e.g. Steam), this also has costs. So the reasoning that you'd save that 30% would be unreasonable.