If Killing Floor 2 generated the same gross revenue on the Epic Games Store, Tripwire Interactive would keep approximately $55,349,337 - that's $8,140,849 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $7,411,273. 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 $43,932,427.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.