The ROI is the free software

Every good work of software starts by scratching a developer's personal itch.

You don't have to pay people to scratch their own itch. However, you do have to pay people to write/work on inferior software.

https://en.m.wikipedia.org/wiki/Business_models_for_open-source_software

https://en.m.wikipedia.org/wiki/The_Cathedral_and_the_Bazaar