If Cyberpunk 2077 generated the same gross revenue on the Epic Games Store, CD PROJEKT RED would keep approximately $687,417,270 - that's $65,601,570 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $93,602,355. 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 $546,713,737.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.