If Slime Rancher 2 generated the same gross revenue on the Epic Games Store, Monomi Park would keep approximately $21,483,718 - that's $3,776,004 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $2,793,234. 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 $16,993,867.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.