If ASTRONEER generated the same gross revenue on the Epic Games Store, System Era Softworks would keep approximately $56,259,189 - that's $8,223,563 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $7,535,344. 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 $44,656,173.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.