If Five Nights at Freddy's: Security Breach generated the same gross revenue on the Epic Games Store, Steel Wool Studios would keep approximately $53,757,096 - that's $7,996,100 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $7,194,149. 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 $42,665,872.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.