Price is only part of the information we get from observing an exchange. The other part is the volume of the goods traded per unit time, called the rate of purchase or sale. From this additional information we understand the extent of the market and the elasticity of the demand and supply.
The concept of price is central to microeconomics where it is one of the most important variables in resource allocation theory (also called price theory). Price is also central to marketing where it is one of the four variables in the marketing mix that business people use to develop a marketing plan.
In general terms price is the result of an exchange or transaction that takes place between two parties and refers to what must be given up by one party (i.e., buyer) in order to obtain something offered by another party (i.e., seller).
Yet this view of price provides a somewhat limited explanation of what price means to participants in the transaction. In fact, price means different things to different participants in an exchange:
Example - Price is commonly confused with the notion of cost as in “I paid a high cost for buying my new plasma television”. Technically, though, these are different concepts. Price is what a buyer pays to acquire products from a seller. Cost concerns the seller’s investment (e.g., manufacturing expense) in the product being exchanged with a buyer. For marketing organizations seeking to make a profit the hope is that price will exceed cost so the organization can see financial gain from the transaction. Finally, while product pricing is a main topic for discussion when a company is examining its overall profitability, pricing decisions are not limited to for-profit companies. Not-for-profit organizations, such as charities, educational institutions and industry trade groups, also set prices, though it is often not as apparent . For instance, charities seeking to raise money may set different “target” levels for donations that reward donors with increases in status (e.g., name in newsletter), gifts or other benefits. While a charitable organization may not call it a price in their promotional material, in reality these donations are equivalent to price setting since donors are required to give a contribution in order to obtain something of value
Economists view price as an exchange ratio between goods that pay for each other. In case of barter between two goods whose quantities are x and y, the price of x is the ratio y/x, while the price of y is the ratio x/y.
This however has not been used consistently, so that old confusion regarding value frequently reappears. The value of something is a quantity counted in common units of value called numeraire, which may even be an imaginary good. This is done to compare different goods. The unit of value is frequently confused with price, because market value is calculated as the quantity of some good multiplied by its nominal price.
Theory of price asserts that the market price reflects interaction between two opposing considerations. On the one side are demand considerations based on marginal utility, while on the other side are supply considerations based on marginal cost. An equilibrium price is supposed to be at once equal to marginal utility (counted in units of income) from the buyer's side and marginal cost from the seller's side. Though this view is accepted by almost every economist, and it constitutes the core of mainstream economics, it has recently been challenged seriously.
There was time when people debated use-value versus exchange value, often wondering about the Diamond-Water Paradox (paradox of value). The use-value was supposed to give some measure of usefulness, later refined as marginal benefit (which is marginal utility counted in common units of value) while exchange value was the measure of how much one good was in terms of another, namely what is now called relative price.
It is now becoming clear that the distinction is not useful and indeed hides a major confusion. The conventional wisdom is that proportional change in all nominal prices does not affect real price, and hence should not affect either demand or supply and therefore also should not affect output. The new criticism is that the crucial question is why there is more money to pay for the same old real output. If this question is answered, it will show that dynamically, even as the real price remains exactly the same, output in real terms can change, just because additional money allow additional output to be traded. The supply curve can shift such that at the old price, the new higher output is sold. This shift if not possible without additional money.
From this point of view, a price is similar to an opportunity cost, that is, what must be given up in exchange for the good or service that is being purchased. For example, if x=1 and y=2, the relative price of x in terms of y is 2, and the price of y in terms of x is 0.5.
The price of an item is also called the price point, especially where it refers to stores that set a limited number of price points. For example, Dollar General is a general store or "five and dime" store that sets price points only at even amounts, such as exactly one, two, three, five, or ten dollars (among others). Other stores (such as dollar stores, pound stores, euro stores, 100-yen stores, and so forth) only have a single price point ($1, £1, €1, ¥100), though in some cases this price may purchase more than one of some very small items
In Marxian economics, the increasing use of prices as a convenient way to measure the economic or trading value of labor-products is explained historically and anthropologically, in terms of the development of the use of money as universal equivalent in economic exchange. However, in an anthropological-historical sense, Marxian economists argue a "price" is not necessarily a sum of money; it could be whatever the owner of a good gets in return, when exchanging that good. Money prices are merely the most common form of prices.
Marxian economists distinguish very strictly between real prices and ideal prices. Real prices are actual market prices realized in trade. Ideal prices are hypothetical prices which would be realized if certain conditions would apply. Most equilibrium prices are hypothetical prices, which are never realized in reality, and therefore of limited use, although notional prices can influence real economic behavior.
According to Marxian economists, while all labor-products existing in an economy have economic value, only a minority of them have real prices; the majority of goods and assets at any time are not being traded, and they have at best a hypothetical price. Six criticisms Marxian economists make of neoclassical economics are that neoclassical price theory:
Most marginalist economists dismiss Marxian theories of price, arguing that those theories require a method of converting from labour values into monetary prices, and that the method given in Marx's Capital (Volume 3) is mathematically flawed. Marxian economists themselves argue that it is impossible to convert values into prices because that attempt involves a conceptual confusion. In certain abstract models, Marx compares quantities of value with price quantities, but he does so, only because of the reality that goods may be traded above or below their value, and the reality that a quantity of value is produced before it is known how much of that value will be realised as income through sales. It would be more correct to say that Marx lacked a theory of short-term price movements.
As William Barber put it, human volition, the human subject, was "brought to the centre of the stage" by marginalist economics, as a bargaining tool. Neoclassical economists sought to clarify choices open to producers and consumers in market situations, and thus "fears that cleavages in the economic structure might be unbridgeable could be suppressed".
Without denying the applicability of the Austrian theory of value as subjective only, within certain contexts of price behavior, the Polish economist Oskar Lange felt it was necessary to attempt a serious integration of the insights of classical political economy with neo-classical economics. This would then result in a much more realistic theory of price and of real behavior in response to prices. Marginalist theory lacked anything like a theory of the social framework of real market functioning, and criticism sparked off by the capital controversy initiated by Piero Sraffa revealed that most of the foundational tenets of the marginalist theory of value either reduced to tautologies, or that the theory was true only if counter-factual conditions applied.
One insight often ignored in the debates about price theory is something that businessmen are keenly aware of: in different markets, prices may not function according to the same principles except in some very abstract (and therefore not very useful) sense. From the classical political economists to Michal Kalecki it was known that prices for industrial goods behaved differently from prices for agricultural goods, but this idea could be extended further to other broad classes of goods and services.