If Little Witch in the Woods generated the same gross revenue on the Epic Games Store, SUNNY SIDE UP would keep approximately $3,814,970 - that's $875,789 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $383,860. 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 $2,939,181.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.