The price is not the seller’s minimum
A seller’s minimum acceptable price is usually tied to what it costs to provide one more unit—not simply the total cost of running the business. For a bakery, the extra flour, labor, and energy needed for another loaf help determine whether making that loaf is worthwhile. If a customer pays more than that added cost, the difference is producer surplus on that sale.
How the gap adds up
Imagine a market price of $5 for a loaf. A bakery would have been willing to sell one additional loaf for $3, so that sale creates $2 of producer surplus. If it sells many loaves, the surplus from each sale accumulates. Other loaves may have different added costs, so their contributions can differ even though customers pay the same market price.
Economists often show this on a supply-and-demand graph: producer surplus is the area above the supply curve and below the market price. The supply curve represents the minimum prices sellers need to supply different quantities.
Surplus is not the same as net profit
Producer surplus helps measure what sellers gain from trading at the market price, but it does not automatically mean that amount is take-home profit. A business may still need to cover fixed expenses such as rent, equipment, or insurance. Those costs are not necessarily part of the cost of producing one extra unit.
That distinction matters when prices change: a higher price can increase producer surplus, but whether a particular business ends up profitable also depends on its full costs.
