If JoJo's Bizarre Adventure: All-Star Battle R generated the same gross revenue on the Epic Games Store, CyberConnect2 Co. Ltd. would keep approximately $15,061,437 - that's $2,827,258 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,917,469. 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 $11,885,234.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.