> No, the idea behind prices is that they are what the participants in particular trades think it is worth trading at.
Why are these two things mutually exclusive? Aren't they, in fact, mutually dependent?
They aren’t. They are different, and one is actually the “idea behind prices in a market economy”, and the other is an academic argument, observing the fact of price setting in a market economy, for why price setting in a market economy is valuable to others besides the direct participants in the individual exchanges.
> Aren’t they, in fact, mutually dependent?
No, there is a one-way dependency between them. The normative argument depends on the fact, but not vice-versa.