If Yes, Your Grace generated the same gross revenue on the Epic Games Store, Brave At Night would keep approximately $5,507,673 - that's $1,222,024 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $614,683. 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 $4,285,649.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.