"The product of mental labor - science - always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production"

Karl Marx's quote is referring to the concept that the worth of science is not accurately reflected in its production. He is saying that the labor-time essential to replicate science is not equivalent to the labor-time needed for its original production. This implies that the amount of work put into developing a scientific discovery is not accurately reflected in the amount of work it takes to recreate it. This is due to the fact that the original production of science requires a good deal of psychological labor, which is not considered when recreating it. Marx is suggesting that the value of science is not properly reflected in its production, and that the labor-time necessary to reproduce it does not properly show the labor-time needed for its initial production. This is an essential principle to think about when looking at the worth of science and its production.