I know for the law journal that I used to edit the journal owned the final form of the edited and stylised work and granted the author a license to freely use it in perpetuity with attribution as to the original publication.

So the author was free to share free copies as long as it was in the original form with the journal's name and logo on the first page, or manuscript forms as long as the original publication info was cited. My journal sold electronic and print fornats and had some licensing deals with legal research companies. But we also hosted free electronic copies for anyone that wanted to download an article

For my journal, the significant costs were paid by a foundation and the university that it was a part of. The sales were just to buy like coffee for the office and stuff help offset costs. I know especially in medicine and physical sciences there's a lot more money involved in this stuff.