Refutations of the labor theory of value often start with a claim that LTV means that if a laborer slacks off and is super inefficient in their production, that this will somehow make the commodity they produce more valuable. Another version of this argument is the claim that LTV means that the quality of the commodity doesn’t affect it’s value, or that literally useless commodities are supposed to have value.

If these people have read Capital, they didn’t get past the first 3 paragraphs, because paragraph 4 is where the discussion of use value begins. It turns out, surprise, commodities actually have to be useful to people and of usable quality to have value, they don’t just magically gain value because someone spent a lot of labor on processing or manufacturing it. A few paragraphs later, we get to discussions about the average labor power of society, and how that correlates to prices of exchange. I think what people get backwards about LVT is that, yes, inefficient productivity CAN cause a commodity to be very valuable and have a high price, but only when the average amount of labor required to produce or extract it is very high.

Marx’s example of diamond extraction is prescient: diamonds were legitimately quite difficult to extract from the earth in that era, and so their value was high. In our modern age, automation in mining and synthetic diamond production have dramatically increased the productivity of labor of diamond mining, which has made them much less valuable. That’s not because any particular worker was working super slowly and inefficiently, nor is it because of the use value of diamonds decreased (their use value has arguably increased, as they’ve found applications in industrial processes).

(I think it’s not until vol 3 that Marx talks about monopolies, but that’s an obvious elephant in the room when talking about diamonds)

This paragraph is like a three in one:

"Some people might think that if the value of a commodity is determined by the quantity of labour spent on it, the more idle and unskilful the labourer, the more valuable would his commodity be, because more time would be required in its production. The labour, however, that forms the substance of value, is homogeneous human labour, expenditure of one uniform labour power. The total labour power of society, which is embodied in the sum total of the values of all commodities produced by that society, counts here as one homogeneous mass of human labour power, composed though it be of innumerable individual units. Each of these units is the same as any other, so far as it has the character of the average labour power of society, and takes effect as such; that is, so far as it requires for producing a commodity, no more time than is needed on an average, no more than is socially necessary. The labour time socially necessary is that required to produce an article under the normal conditions of production, and with the average degree of skill and intensity prevalent at the time. The introduction of power-looms into England probably reduced by one-half the labour required to weave a given quantity of yarn into cloth. The hand-loom weavers, as a matter of fact, continued to require the same time as before; but for all that, the product of one hour of their labour represented after the change only half an hour’s social labour, and consequently fell to one-half its former value. "