This is only half the story. Several business models around open source are working and proven (e.g. hardware vendors writing kernel drivers) but there is also

This is only half the story. Several business models around open source are working and proven (e.g. hardware vendors writing kernel drivers) but there is also a lot of unpaid volunteer work that everyone seems to take for granted. GIMP is one example. And probably a large number of the packages on NPM. Or think about OpenSSL, everyone was just assuming it must be well-funded, while nobody was actually funding it.