If God of War generated the same gross revenue on the Epic Games Store, Santa Monica Studio would keep approximately $130,514,617 - that's $14,974,056 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $17,661,084. 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 $103,722,991.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.