Your argument doesn't take into account power dynamics. When negotiating price, each side comes to the table with bargaining power. If bargaining power is sufficiently uneven then you really can't claim they'll come to a fair agreement.
When an amazon warehouse worker has to pee in bottles to meet a quota do you think the worker and amazon came to a fair agreement? Or perhaps amazon had more bargaining power.
Worth and value are inherently subjective. Price is an attempt to assign an objective value to something subjective. It kinda/sorta works, but it also kinda doesn't.
Let's imagine there is no minimum wage in America. Now let's say that workers in America demand $10/hour and African workers ask for $2/hour for the exact same job. What's the correct value for that labor? It's a non-sensical question.
You could say it's the minimum value at $2. But then some other worker asks for $1. Did you make a mistake? Was it not actually worth $2 the whole time?