If Mini Motorways generated the same gross revenue on the Epic Games Store, Dinosaur Polo Club would keep approximately $4,920,288 - that's $1,101,877 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $534,585. 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 $3,818,411.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.