> Art is the big gap here. Few could argue successfully that the world is not a better place for the creations of JS Bach, Kafka, Keats, Van Gogh, yet these people did not make their fortune from their life's passion and work. Only after their death were they appreciated for what they did in their figurative basements.
You're taking the exceptions (and actually Bach earnt quite well from music). Van Gogh was almost unique among his painting contemporaries, partly because his paintings were, by the standards of the time, weird (I suspect this applies to Kafka as well). And what vindicates him now is an ultimately capitalist consideration - his works are popular, people pay for copies of them. Nowadays there are capitalistic art speculators who will buy the work of underappreciated artists if they like it themselves - see the recent https://news.ycombinator.com/item?id=8829277 - which would solve that problem.
As for Kafka, he had a famously... weird approach to his work. IIRC he wanted his works destroyed; it's only the capitalism of his descendants that means we're able to appreciate them.