If Frostpunk 2 generated the same gross revenue on the Epic Games Store, 11 bit studios would keep approximately $20,456,376 - that's $3,624,237 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $2,653,142. 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 $16,176,663.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.