If The Stanley Parable: Ultra Deluxe generated the same gross revenue on the Epic Games Store, Crows Crows Crows would keep approximately $13,421,691 - that's $2,585,023 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,693,867. 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 $10,580,891.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.