Value here is a proxy for predicted success which then translates to access to resources. Not directly, but markets with lots of predicted success then have access to investor capital. Also companies can own their own shares, and often do use those shares to get access to new capital, and companies can be purchased by larger companies, giving them more capital to work with.
I agree it's pretty stupid, but it works. Check out prediction markets for example. That's not to say that it's efficient by any stretch, but allocation of resources is NP hard, and this algorithm works well with humans.
As capricious as markets are, that's a pretty loose definition of "works". All too often, equity markets are just a force multiplier for herd mentality, and end up being actively antithetical to actual value and resource allocation.
One other property of markets is that they're very good at transferring wealth from those who get caught up in the herd mentality to those who do their own research and hold their own opinions. This may be bad for wealth inequality, but it does make them self-correcting when it comes to human emotions.
In corporate finance, valuation has a specific meaning. In this case, lost half of its value is correct; even better would be "market value".
Book value is the term for assets minus liabilities, so “value” without qualification tends to imply all types of value at once. The term “company value” used at the end of the article might even tend to imply more book value than market value to the average techcrunch reader. I suspect the author intended to conflate them in order to paint a picture that is more negative than the real story.
He definitely conflated market value with book value when he wrote “Nvidia is proving that an otherwise strong technology business can disappear in the blink of an eye.” That line is more or less pure hyperbole.
Production is what most humans spend their working days doing or supporting or contributing to.
In the case of company value, investors care not only about what the company is worth today but also about what it will be worth in the future. It makes sense that lower sales result in a lower stock price despite the fact that the products and current capital are unchanged.
Example, people can value something very highly but not have funds to buy it, someone who can afford the price easily can value something as being of little worth, but due to their wealth they can afford it.
You appear to be confusing price, ability to pay, and value.
Do look at art. You can buy a hugely influential piece of art and not value it at all, you buy it as an investment but don't care about its innate qualities, its influence on the art world (directly, only indirectly by the price that confers) or it's cultural worth.