Gotta agree, I never understand the hard work argument regarding worth. Just because someone works hard doesn't mean it's a profitable endeavor. I worked hard at startups that failed, it doesn't mean the startup has to be worth anything.
Until the United States economy no longer recognizes intellectual property rights, this is a critical distinction, whether we're discussing books, music, or proprietary software and hardware designs.
The labor theory of value is obviously complete bunk, but it sticks around anyway because it's a central tenet of Marxism.
More likely: it sticks around as a tenet of Marxism because it's a thing many people find intuitively plausible. "I did all this hard work, so I should be rewarded" is a pretty natural thing to think.
Is it really? I rolled a boulder up and down a hill all day, pay me.
"Nobody asked you to do that and nothing productive was accomplished. Nobody will pay you for that."
But I worked really hard! Labor creates value, therefore I am entitled to payment.
Whether you're rolling a boulder or writing a book, your labor hasn't created value unless you've actually produced something other people subjectively believe to be valuable. The subjective theory of value is common sense. The labor theory of value is obvious bullshit. It might fool children but for an adult to believe it requires brainwashing.
This is also the crux of why I cannot understand how people follow LTV. It just doesn't make sense upon even the slightest introspection.
If you want to volunteer for homeless shelters or something, then you can sleep sound with the knowledge that what you're doing is worth a great deal to people who can't afford to compensate you for it. But writing books nobody wants to buy is not that sort of selfless act of charity.