If Kingdom Two Crowns generated the same gross revenue on the Epic Games Store, Stumpy would keep approximately $3,355,261 - that's $781,758 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $321,172. 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 $2,573,503.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.