If E.Y.E: Divine Cybermancy generated the same gross revenue on the Epic Games Store, Streum On Studio would keep approximately $2,029,161 - that's $510,510 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $140,340. 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 $1,518,651.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.