You're really missing one part about Valve. Game developers that publish games on Steam are not allowed to set lower prices on other stores; at least on release

You're really missing one part about Valve. Game developers that publish games on Steam are not allowed to set lower prices on other stores; at least on release when bulk of sales happening and most of full price sales occur. So developer can't sell game on Steam for $60 and at the same time sell it on Epic Games Store for $50 due to lower commission. So Epic don't have any other tools to compete with Steam.