Only the marginal consumer is willing to pay just the market price in a typical supply and demand equilibrium. The consumers would be willing to pay more than the market price are what makes the demand curve slope downward. The amount that these consumers would be willing to pay, but do not have to pay is known as the consumer surplus.
The diagram below is borrowed from Who Pays a Sales Tax?, which applies this concept.
Classic Economic Models
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Balance of Payments
Endogenous Technical Change
Federal Funds (Fed Funds) Rate
Fixed Exchange Rate
Floating Exchange Rate
Gross Domestic Product (GDP)
Production Possibility Frontier
Reservation Wage Rate
Theory of the Consumer
Theory of the Firm
Velocity of Money