If Killer is Dead - Nightmare Edition generated the same gross revenue on the Epic Games Store, KADOKAWA GAMES / GRASSHOPPER MANUFACTURE would keep approximately $2,816,923 - that's $671,643 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $247,762. 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 $2,145,279.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.