And there is one problem: "belief". Some people can walk through Xerox PARC and bet their company on 3-4 things they see. Others can own Xerox PARC and bet their company on 3-4 largely different things.
In EMH there is cooked in some notion of overall largely rational beliefs, and yet the shares trade hands from someone selling to someone buying - both of which feel they got a good deal worth making money from.
i mean, if you want to go all epistemological, sure, let me rephrase. each of us individual humans live in a specific world mapped on what we believe we know and our lived experience, and there is (at least) one unique world for each individual human. the price is a representative agent of a subset of the worlds that exist within the minds of the participants of the economy. as the mappings of reality upon the beliefs and experiences of the individual participants change, the price changes.
"Belief" being the key word.
The economy is a faith-based construct. Prices aren't set by "information", but by faith in value - which is one of the easiest things in the world to lie about.
This isn't related. You're zooming way out to "how do we know anything, man?" This is far more specific a topic than that.
emh doesn't mean everyone knows everything, it means the price accurately reflects available information. if an innovation was believed to be world changing, it would be worth a lot, if the belief changes, the price changes.