If Grand Theft Auto: Vice City – The Definitive Edition generated the same gross revenue on the Epic Games Store, Rockstar Games would keep approximately $6,713,629 - that's $1,468,697 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $779,131. 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 $5,244,932.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.