For the record, when Epic did their stunt on August 13, 2020, the margin went to the user.
> Today, we’re also introducing a new way to pay on iOS and Android: Epic direct payment.
> When you choose to use Epic direct payments, you save up to 20% as Epic passes along payment processing savings to you.
https://www.epicgames.com/fortnite/news/the-fortnite-mega-dr...