Epic wasn't fined for putting things on sale. Instead, it was fined for putting pressure on children to buy things that were put on sale; e.g. through wording like "Get it now" and "Grab it", and through design.
This makes no sense. You can't buy anything on Fortnite with real money. The purchase you make is for blocks of v-bucks which can then be spent on items.
The actual financial transaction is completely divorced from any items that are on sale and, hopefully, that financial transaction is completely out of the direct control of children.
For details, check the ruling here (Dutch): https://uitspraken.rechtspraak.nl/details?id=ECLI:NL:RBROT:2...