If Bendy and the Dark Revival generated the same gross revenue on the Epic Games Store, Joey Drew Studios would keep approximately $6,063,297 - that's $1,335,674 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $690,450. 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 $4,727,623.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.