Labour Theory of Value

The labor theory of value (LTV) is a theory of value that argues that the economic value of a good or service is determined by the total amount of socially necessary labor required to produce it, rather than by the use or pleasure its owner gets from it. At present, this concept is usually associated with Marxian economics, although it is also used in the theories of earlier liberal economists such as Adam Smith and David Ricardo and later also in anarchist economics.

When speaking in terms of a labor theory of value, value, without any qualifying adjective should theoretically refer to the amount of labor necessary to produce a marketable commodity, including the labor necessary to develop any real capital used in the production. Both David Ricardo and Karl Marx tried to quantify and embody all labor components in order to develop a theory of the real price, or natural price of a commodity. However, the labor theory of value as presented by Adam Smith did not require the quantification of past labor—nor did it deal with the labor needed to create the tools (capital) that might be used in producing a commodity. Smith's theory of value was very similar to the later utility theories in that Smith proclaimed that a commodity was worth whatever labor it would command in others (value in trade) or whatever labor it would "save" the self (value in use), or both. But this "value" is subject to supply and demand at a particular time.

The real price of every thing, what every thing really costs to the man who wants to acquire it, is the toil and trouble of acquiring it. What every thing is really worth to the man who has acquired it, and who wants to dispose of it or exchange it for something else, is the toil and trouble which it can save to himself, and which it can impose upon other people. (Wealth of Nations Book 1, chapter V)

Smith's theory of price (which for many is the same as value) has nothing to do with the past labor spent in producing a commodity. It speaks only of the labor that can be "commanded" or "saved" at present. If there is no use for a buggy whip, then the item is economically worthless in trade or in use, regardless of all the labor spent in creating it.

...
Wikipedia