If Stray generated the same gross revenue on the Epic Games Store, BlueTwelve Studio would keep approximately $78,013,941 - that's $10,201,267 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $10,501,901. 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 $61,961,090.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.