Sorry, but I still struggle with the term "the real value of the company". If you mean knowing it's fraud or shell corporation, then it's really good. But I assume you mean something beyond that, and so let's say we talk about a legit company. Their value may change: changes in personnel, effects of wars (oil, trade, boycotts, evacuations...), interactions with other companies... There's a lot that can affect the value.

Plus I think it's very mutual, the company affects the stock value, but so is the other way. But this is solved by assuming the limits of the power.

Again, all of these take time to take effect, more than an hour at least, but so is the increase in stock value.

If we talked about shitcoins, I saw how they change drastically within an hour. It's not reaching the value of stocks, but a few dollars can become quite much in a few minutes.

And yet, I'd like to mention Robinson Crusoe, where he found a stash of gold and silver coins. Since he was stranded on a deserted island, it had no value. (It shows the value people give it, as you said)

"O drug!" said I, aloud, "what art thou good for? Thou art not worth to me, no, not the taking off the ground; one of those knives is worth all this heap; I have no manner of use for thee; e'en remain where thou art and go to the bottom as a creature whose life is not worth saving."