If ShellShock Live generated the same gross revenue on the Epic Games Store, kChamp Games would keep approximately $5,581,648 - that's $1,237,155 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $624,770. 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 $4,344,493.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.