In order to understand properly how Marx “solves” the problem it is necessary to point out that his surplus value theory was based on the Ricardo’s value theory. Nevertheless, Marx criticized it because for him it was impossible to agree that mutual equivalent exchange of embodied value for labor (as a salary) and Ricardo’s labor value are the same notions. According to Marx, labor is the ability to create value, which is the total labor hours. Marx also investigated the relations between the articles of merchandise and money. He stated that merchandise exchange must generate money. He investigated the process of transforming money into capital and proved that it is dependent on the wage workers employment. Consequently, Marx started using the category of labor-power, which meant the ability to work instead of just labor. Labor-power is unique because it has value and generates value. Thus, not labor, but labor-power is a unique commodity. The price for labor-power is equal to labor, which is necessary to produce it. As a result, we see that purchase and sale of labor-power in terms of such price for it are not in conflict with the value theory.
Some scholars criticized Marxist economics, considering it to be unessential and his ideas to be unproven. At the same time some supported it and finally it has become a part of an official ideology almost in all socialistic countries. To my mind, Marx’s theory is quite complicated, but very appropriate for the period of early industrialization, which we can find nowadays in some countries with cheap labor-power like China, India, Turkey. The statement that workers sell their ability to work, that labor hours are the value sounds logical to me and I support this idea. Labor itself can not posses value as the gravitation itself can not posses its own weight. Labor is the process during which the value is created. Marx’s statement that the price for the articles of merchandise does not equal the price for the labor-power is also true.