In this selection from The Wealth of Nations, Adam Smith discusses prices in terms of labor and happiness.

Adam Smith was a Scottish political philosopher and economist, considered one of the forefathers of classical economics and a pioneer of the study of political economy. Smith graduated from Balliol College at Oxford, and later served as the chair of moral philosophy at the University of Glasgow. He departed from his academic position after 12 years to tutor the Duke of Bucchleuch in Switzerland. His two major works, An Inquiry into the Nature and Causes of the Wealth of Nations, and The Theory of Moral Sentiments, were composed after he left the service of the Duke on a lifetime pension.
The former work, considered his magnum opus, is often referred to by its abridged title The Wealth of Nations. It was first published in 1776, the same year as the American Declaration of Independence, and is considered a foundational text in modern economic theory. It is noted for its influence on the American founding fathers James Madison, Alexander Hamilton, and Thomas Jefferson, and upon the economic theories of Karl Marx, John Maynard Keynes, and Milton Friedman.
The latter work expressed Smith's deep interest in moral philosophy, and expanded upon the philosophical, juridical and ethical framework of his earlier work. While known primarily as an economist today, Smith's work and interests lay primarily in the fields of theology, jurisprudence, and moral philosophy.

As it is the power of exchanging that gives occasion to the division of labour, so the extent of this division must always be limited by the extent of that power, or in other words, by the extent of the market. When the market is very small, no person can have any encouragement to dedicate himself entirely to one employment, for want of the power to exchange all that surplus part of the produce of his own labour, which is over and above his own consumption, for such parts of the produce of other men’s labour as he has occasion for…

Every man is rich or poor according to the degree in which he can afford to enjoy the necessaries, conveniences, and amusements of human life. But after the division of labour has once thoroughly taken place, it is but a very small part of these with which a man’s own labour can supply him. The far greater part of them he must derive from the labour of other people, and he must be rich or poor according to the quantity of that labour which he can command, or which he can afford to purchase. The value of any commodity, therefore, to the person who possesses it, and who means not to use or consume it himself, but to exchange it for other commodities, is equal to the quantity of labour which it enables him to purchase or command. Labour, therefore, is the real measure of the exchangeable value of all commodities.

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.

People of the same trade seldom meet together, even for merriment and diversion, but the conservation ends in a conspiracy against the public, or in some contrivance to raise prices. It is impossible indeed to prevent such meetings, by any law which either could be executed, or would be consistent with liberty and justice. But tough the law cannot hinder people of the same trade from sometimes assembling together, it ought to do nothing to facilitate such assemblies; much less to render them necessary.