If Persona 5 Royal generated the same gross revenue on the Epic Games Store, ATLUS would keep approximately $113,921,498 - that's $13,465,591 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $15,398,386. 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 $90,523,919.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.