Thats actually what valve does. Valve mandates all games on platforms must be the same retail price (e.g a game on Steam cannot be sold for 60$ retail, but be sold for 50$ on epic), not including deals and sales.

Its standard with how physical stores demand that digital copies of games must retail at the same price as physical else stores would see that as an attack on the business by the company.

There is essentially some level of price normalization.

it's not