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.
