fair points. still i invite you to study Blender's funding model. it's the best success story i can think of. they started out as just an open-source project that volunteers contributed code to.

then they produced open movies, books, merch to support development. also offered paid consultancy, until they were able to afford a new location and a few full-time developers (their store seems to be down for now).

so, it can be done, just needs a bit of effort and i'm sure many of us will gladly pay for products that have a side-effect of supporting developers.

https://www.blender.org/get-involved/