[Nasrudith]

Yeah even putting aside demand (just because someone spent 50 years making one really good vase doesn't mean 50 years of pottery wouldn't be better even if the potter had to dredge all of the clay themselves instead of using apprentices or hired servants) it has been obviously broken since the Industrial revolution at least but had predecessor cases that pointed out it wasn't true. Aquaducts or irrigation canals alone snap it in half.

It goes from "effort to haul X ammount of water Y distance by N people" to "and it just flows after this constant work".

[blts]

You mistakenly equate effort with value.

[randallsquared]

They're explicitly arguing against equating effort (labor) with value.