If Plants vs. Zombies™ Garden Warfare 2: Deluxe Edition generated the same gross revenue on the Epic Games Store, PopCap would keep approximately $18,037,629 - that's $3,266,922 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $2,323,313. 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 $14,252,659.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.