If Far Cry® 5 generated the same gross revenue on the Epic Games Store, Ubisoft Montreal would keep approximately $145,990,980 - that's $16,380,998 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $19,771,497. 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 $116,033,734.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.