If KINGDOM HEARTS -HD 1.5+2.5 ReMIX- generated the same gross revenue on the Epic Games Store, Square Enix would keep approximately $8,697,811 - that's $1,874,552 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,049,702. 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 $6,823,259.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.