If Tomb Raider Game of the Year generated the same gross revenue on the Epic Games Store, Crystal Dynamics would keep approximately $67,798,940 - that's $9,272,631 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $9,108,946. 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 $53,835,520.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.