If The Legend of Heroes: Trails in the Sky generated the same gross revenue on the Epic Games Store, Nihon Falcom would keep approximately $4,500,405 - that's $1,015,992 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $477,328. 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 $3,484,413.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.