If The Beast Inside generated the same gross revenue on the Epic Games Store, Illusion Ray would keep approximately $6,622,255 - that's $1,450,007 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $766,671. 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 $5,172,248.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.