Oh my lord. The problem isn't the pricing!!!!!! If you feel like you can't sell your game for $55 on just Epic so you must sell it on Steam too but for $70, there's a problem with your product and/or service. Not Steam. Epic tried the "1 year exclusivity" for a couple of games, like Borderlands 3 did that. People simply didn't buy the game. Was the game cheaper? Nope.
See my point? Steam had zero hand in people rather not buy a game than installing Epic.