If Tomb Raider I-III Remastered Starring Lara Croft generated the same gross revenue on the Epic Games Store, Aspyr, Crystal Dynamics would keep approximately $4,826,699 - that's $1,082,734 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $521,823. 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 $3,743,965.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.