Selling game assets between players

I’m going to make a game where players can sell game assets to each other for real money. The developer will not take commission and will not earn from this process. The monetization model will be paid entrance or in-game purchases.
Will the sale of assets between players be considered as a developer money flow? Will the developer need to pay 5% from these operations to Epic? In this scheme, the use of the UE is not profitable, because the developer earnings will be much less cash flow between players.

Can you please expand on what kind of assets will be sold and how such assets are created?

For example, a sword. The player can craft it or buy it from another player.

Thanks, can you also please expand on your monetization model? What do you mean by paid entrance?

The developer will earn with:

  • the game will be paid (digital download)

  • micro-transactions (cosmetic-only)

The developer will not earn with:

  • player trading

Thanks. The developer will not owe royalties for the value of trading in-game items between players.