Or more simply, it ignores that the sum of an hour of labor does not exist in a vacuum, but is instead a product of the time and effort the laborer had previous

Or more simply, it ignores that the sum of an hour of labor does not exist in a vacuum, but is instead a product of the time and effort the laborer had previously invested in their craft. There's the old joke about the repairman who charges $200 to replace a bolt. Outraged, the customer says "that's it?! how can you charge $200 for that?!", and the repairman answers "Well, that's $0.15 for the bolt, and $199.85 for knowing where to put it."