It’s still stealing if the profit is this extremely high. Of course a successful business includes providing a useful product. But if you make so much more money per employee than any other company, that means the amount you’re charging is disproportional. They could change Steam fees to 5% and still be extremely profitable. They choose not to because of greed.
This is not me condemning them by the way, I think their greed and what they do with the money available to them is still mostly better than what other people do, but it’s still greed.
I define all excessive profit as stealing. In an ideal world everyone would be earning roughly the same. (Or no earning being necessary at all, but I don’t want to go into every detail)