Consumer surplus
Consumer surplus is the difference between what buyers are willing to pay and what they actually pay.
You would have paid more for plenty of things than you actually did. That gap, summed across everyone, is consumer surplus.
Consumer surplus is the difference between what buyers are willing to pay for a good and what they actually pay. It is the value buyers capture from a transaction beyond its price, a rough measure of the benefit a market delivers to the people who buy in it.
The value beyond the price
In any market, different buyers value a good differently. Some would pay far more than the going price; others only just enough to buy at all. Everyone who buys at a single market price, except the very last marginal buyer, gets the good for less than it was worth to them. The accumulated value of all those bargains is consumer surplus, and it represents real welfare even though no extra money changes hands to reflect it.
Why it matters for policy and pricing
Consumer surplus is central to judging whether markets and policies make people better off. A change that raises consumer surplus, lower prices, more competition, a better product, benefits buyers even if it is invisible on any firm's accounts. Economists use it, alongside producer surplus, to assess the total welfare a market generates and the deadweight loss when something, a tax or a monopoly, prevents mutually beneficial trades.
The firm's eye on it
For a business, consumer surplus is both a sign of value delivered and a target. A firm that charges a single price leaves surplus in customers' hands; price discrimination, charging each buyer closer to their willingness to pay, is in effect an attempt to convert consumer surplus into profit. That tension, between the buyer keeping the surplus and the seller capturing it, lies behind much of pricing strategy.
Consumer surplus makes visible something easy to overlook: that a price is not the same as a value, and that functioning markets routinely hand buyers more than they pay for. Measuring it, however roughly, is how economists put a number on benefits that the cash flows alone never show.