If Total War: SHOGUN 2 generated the same gross revenue on the Epic Games Store, CREATIVE ASSEMBLY, Feral Interactive (Mac), Feral Interactive (Linux) would keep approximately $40,694,816 - that's $6,614,007 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $5,412,930. 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 $32,275,422.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.