The problem is we can use that to determine the belief of the zeitgeist: if you--or anyone else--truly believes Twitter is worth more than $45--and has any hope of getting to that value in the not-distant future (of course: time is also money)--you should go buy it, as there are apparently a number of suckers right now willing to accept a mere $45 for their shares. People trade because they think things, and if no one is trading right now it "should be" because they largely agree with the zeitgeist.

(This is also why we can use this price to indirectly learn something about how the market views the likelihood of Elon buying Twitter: if it were a "sure thing", the price of Twitter stock would be trading close to $55, as you'd be able to make a fast profit.)

It's not that binary though. Imagine you belief Twitter is worth 45.01USD but it's trading 45USD, would you throw your life savings at it (disregarding fees), no, of course not, way too risky!

The way I see it, people (and other entities!) don't think Twitter is worth X, they think there is a distribution of worth.

This means there is risk in their bet, so if I thought Twitter was worth (on average) 100USD, that wouldn't mean I would sink my life savings into it but would put in some, based on the risk and also what else I need capital for.

Also, how much one thinks Twitter is worth probably also depends on your time horizon: like the old adagium that the market can stay stupid for longer than you can stay solvent, e.g. when shorting a scam.

In short, the reason you wouldn’t buy it right now, despite believing its outlook is rosy, is because you think it’ll go lower in the short to medium term. Which is more or less what all the analysts are predicting about tech stocks broadly.

If a non-zero number of people thought it was a good idea to buy it at $60 a non-zero number of people would sell it at $60. The large number of actors each trying to outsmart each other acts as a dynamic value-setting strategy.