If Sonic & All-Stars Racing Transformed Collection generated the same gross revenue on the Epic Games Store, Sumo Digital would keep approximately $7,972,481 - that's $1,726,189 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $950,793. 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 $6,246,292.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.