30% of which already go to Steam in the case of Garry. Plus wages, taxes, rent, equipment. You add another 10-20%+ on top which you can’t predict now because of Unity. Plus all the paid libraries and licenses already charging per seats or game revenue.
That being said, devs like Garry absolutely make banks and 400k is not that huge of a chunk for him. He, and a lot of devs, would probably be paying more on a royalty system like UE, which is the real irony here. But yeah, what most people lament is the slimeyness of the move and the terms.