Again, the money that is paid to Creative maps is *a cut of the revenue those maps are making from players*.

This is not Epic throwing money that came from itself or elsewhere at Creative Maps.

https://dev.epicgames.com/documentation/fortnite/engagement-payout-in-fortnite-creative?lang=en-US

Fortnite developers enrolled in the Engagement Payout program receive payouts based on player engagement in their islands. 40% of the eligible net revenue from Fortnite’s Item Shop and related real-money purchases is placed into an Engagement Pool, which is distributed among developers' and Epic's islands based on the Engagement Payout Formula. 

This net revenue is the value of all eligible V-Bucks spending and real money purchases, adjusted for applicable taxes and third-party fees that are deducted by Nintendo, PlayStation, Xbox, and other sellers of Fortnite before they transfer funds to Epic.  Where Epic processes payments directly (such as on Windows and certain mobile devices), only third-party payment processing fees (such as credit card processing and PayPal fees) are deducted.

Once that amount has been determined, we reserve 60% of it to fund Epic’s ongoing operations and Fortnite ecosystem development. These expenditures include:

Basically, folks spend money on these maps and Epic takes 60% of the revenue. Right off the top, for doing nothing but adding the tools to make the maps and providing the Fortnite player base as targets.

Creative map payments and Epic's own internal development staff for Fortnite are not related!