He was, to all intents and purposes, a classical economist, the only difference being that in his case the reasoning became a weapon to attack capitalism rather than a weapon to defend it. Like most of the writers who preceded him, Marx attributed the economic value of commodities to the labor expended on them. This was in essence Ricardo's view. Marx added merely that in order to produce value the labor must be socially necessary, that is, its product must be of use to somebody. Value in exchange, as markets develop, may be measured in money terms, but if all illusions and deceptions of money are penetrated, the consumer who wishes to use an article is merely paying for the socially necessary labor that west into it.
Money is the intermediary.
The capitalist, however, is not buying articles for use, he is buying articles for resale. A cotton-mill owner buys yarn, spindles, and the labor of the spinning operatives. Each of these components of the final product costs him the price of the labor that went into it. But he manages to sell the product of his mill for more than it costs him' If he did not, there would be no profit in the transaction. Therefore he is the recipient of surplus value.