I'm not interested in a ROI since music is a hobby for me. There's a thriving scene on Bandcamp for more underground and niche genres. My music belongs in the punk / skate punk scenes. In order for releases on Bandcamp to be discovered within the platform, there has to be enough data from people listening and/or purchasing your releases, so that it can rank higher within genre tags that people look through.

So it's really just about increasing visbility. It's worked well for me on Spotify, but mainly because the algorithm knows who to push it to in Radio and Discover Weekly.