Yes Valve is very generous.
They take MORE from developers who make LESS money. I sure bottom 98% of developers never sell above $10,000,000 to decrease cut from 30% to 25%.
Very few indie devs or small indie studios ever sell over 50,000-100,000 copies.
PS: In practice if your project funded by publisher it means that you as developer will make less money from a game than Valve.