Why does it not make sense when goods are not fungible? The buyer and seller can ascertain how fungible the good they are interested in exchanging is. If it’s not, then the other prices will not matter as much. But more information is better than less information.

Also, while employees might not be completely fungible (pretty much all are replaceable though on a long enough timeline), the employees are buying money from the employees, and that is fungible.

What's the value of a 1999 Camaro? How much should that number influence the price of last year's minivan?

Arguing about the relevance of information to a transaction for some good is 1:1 with simply arguing about the transaction price for some good. Just haggle directly instead of in some meta fashion.

How does a person know which fields to pursue if they do not know wages? You have to look at the trends for which each wages are moving, where they are moving, the number of new job seekers in that field, the number exiting that field.

It is much better now with the internet, but it was not long ago that if you did not know some in a specific business, you had no idea what they would be earning. For a kid in a lower income family, they might never know about what to study to get the top incomes.

> What's the value of a 1999 Camaro? How much should that number influence the price of last year's minivan?

Depends if the buyer is trying to decide between buying a 1999 Camaro or last year’s minivan. Just like a high school student might be trying to decide which field to go into.