If VTOL VR generated the same gross revenue on the Epic Games Store, Boundless Dynamics, LLC would keep approximately $8,991,148 - that's $1,930,511 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,089,702. 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 $7,056,595.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.