If Encased: A Sci-Fi Post-Apocalyptic RPG generated the same gross revenue on the Epic Games Store, Dark Crystal Games would keep approximately $3,536,202 - that's $818,769 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $345,846. 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 $2,717,433.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.