If Ori and the Will of the Wisps generated the same gross revenue on the Epic Games Store, Moon Studios GmbH would keep approximately $57,642,542 - that's $8,349,322 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $7,723,983. 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 $45,756,567.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.