This paper aims to analyze the question of value, searching for the parameters that substantialize its expression. Through the use of the deductive method and the bibliographic review, it is intended to rescue the Marxist elaborations on this subject, thus, characterizing the value as a historical social form pertinent to capitalism. The analysis runs through the production and circulation of commodities, demonstrating, in those fields, the existence of objective conditions that constitute value. During the exposition, the assumptions of labour theory of value are compared to those of the neoclassic school of economy, accountable for the production of the subjective theory of value. In the second part of the paper, we sought to explain the prices of medicines with the Marxist labour theory of value, showing, with that, its pertinence regarding the explanation of social phenomena.