If Pathologic 2 generated the same gross revenue on the Epic Games Store, Ice-Pick Lodge would keep approximately $8,740,475 - that's $1,883,279 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,055,519. 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 $6,857,196.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.