If ARMORED CORE™ VI FIRES OF RUBICON™ generated the same gross revenue on the Epic Games Store, FromSoftware, Inc. would keep approximately $86,868,244 - that's $11,006,204 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $11,709,306. 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 $69,004,285.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.