If Keep Talking and Nobody Explodes generated the same gross revenue on the Epic Games Store, Steel Crate Games would keep approximately $3,811,601 - that's $875,100 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $383,400. 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 $2,936,501.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.