If Space Rangers HD: A War Apart generated the same gross revenue on the Epic Games Store, SNK Games, Elemental Games, Katauri Interactive would keep approximately $2,440,387 - that's $594,625 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $196,416. 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 $1,845,762.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.