Oxygen is very valuable for human life, but the price is free.
It's not always the case that something very valuable is very expensive.
Also value depends on the individual and the area they live
Some people value different things differently, and so on.
Basically there's no single price for something. Every person at different times value everything at different prices.
The markets try to get close to that real value with estimates, and people react accordingly.
I agree, except I see you possibly equivocating between value and price with your "Every person at different times value everything at different prices." A version of this that does not suggests equivocation is "Every person at different times are willing to pay different prices for what they think is a value."
The other thing I would add to what you wrote is is "The market can be mistaken or defrauded about both price and value." That's why an independent person will perform his own analysis to determine both whether something is a value (by figuring out the why) and, once it's determined to be a value, whether the price is a fair one.