They get money from every install of the games and an amount agreed upon beforehand. Epic is using what they would have spent on marketing to give free games, the CEO explained it in an interview.

Do you really think devs would let Epic give their game away for free without getting anything in return? You realize that would be illegal, right?

Freaking hell.

[–] CileTheSane@kbin.social 2 points 1 year ago

Epic CEO Tim Sweeney previously revealed that the company pays a flat fee to each developer to give away their games, rather than paying per download.

https://www.theverge.com/2021/5/4/22418782/epic-games-store-free-games-cost-apple-trial-arkham-subnautica-mutant-year-zero

Your download doesn't give the developer any money. The fee is already paid. The Developer gets just as much from you if you pirate their game, or more if you go purchase it on a different platform instead.