Estimating "true market value" of companies whose valuation is almost entirely based on their potential long-term growth isn't particularly straightforward until you find a buyer willing to buy a significant or it does an IPO.
I fail to see how this is in any way whatsoever relevant. a unique car has a market value, and a non-unique car also has a market value. anything that can be sold has a market value. there's still no such thing as a "true market value"
Well not until you try to sell it and find a buyer.
I mean sure xAI does technically have a market value we just don't know what it is because there is no market that would allow us to determine it.
Of course the price paid by private investors do provide some estimate but a company .e.g. raising $5 billion at a valuation of $150 billions or something like doesn't necessarily have a market value which is that high.
just because you don't know the market value of something doesn't mean it doesn't have one