If Moon Hunters generated the same gross revenue on the Epic Games Store, Kitfox Games would keep approximately $1,893,533 - that's $482,768 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $121,845. 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 $1,410,765.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.