If DARK SOULS™ II: Scholar of the First Sin generated the same gross revenue on the Epic Games Store, FromSoftware, Inc. would keep approximately $66,549,465 - that's $9,159,042 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $8,938,563. 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 $52,841,620.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.