If The NOexistenceN of you AND me generated the same gross revenue on the Epic Games Store, 0x0Real Studio would keep approximately $369,484 - that's $110,845 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $0. Epic charges 0% on the first $1 million in annual per-app revenue and then 12% on the remaining amount. On GOG (30% cut), the developer would earn approximately $258,639.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.