Everyone knows their value prop going in: unless you are able to monetize the complement like RedHat or Google, payment is in experience, reputation, and a fun challenge.
Very idealistic people might not realize this as they start working on their project.
I wish it was otherwise, people, but it's usually "build it and they WON'T come" ("they" being the funds needed to make a living.)
Payment can also appear in the form of collaborators helping improve a tool you want for yourself, especially if you choose the right license.