>If sanitary work stopped today, society would quickly disintegrate, whereas if investors stopped working today the world would be improved.
Society wouldn't disintegrate without sanitary workers. It would get grosser, with people forced to do their own plumbing and dump their own trash. And even if all sanitary workers united and went on permanent strike, they could be quickly replaced within a few months. As I said, there's no shortage of people able and willing to do that job.
If investors all quit we'd be fucked. Maybe not overnight, but eventually. No new investments. No new businesses. No new jobs. The economy stops growing. People can't buy cars or homes because there is no one to lend them money. Businesses can't get loans to invest in new more efficient processes, or new factories, or whatever. And no one can just come in and replace them, because it requires a lot of money and risk tolerance among other things.
>Isn't supply-and-demand nebulous ? It's humans who place values on goods and services, not some law of nature
Not some law of nature, but economics. The prices of things are not arbitrary, they are set based on how strongly people value that thing divided by the supply. If you have a huge supply of people who can do a job, then the wage isn't going to be very high.
And this is a good thing. It creates incentives for people to take the jobs that are most demanded. There is a big demand for programmers and a short supply. If a sanitary worker can switch to programming, the economy would be a bit more efficient. At the moment we need slightly more programmers and slightly fewer sanitary workers. If everyone did this it would eventually equalize and they would pay the same.