If Kane & Lynch 2: Dog Days generated the same gross revenue on the Epic Games Store, IO Interactive would keep approximately $1,593,298 - that's $421,356 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $80,904. 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 $1,171,942.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.