Final answer:
Producer surplus is the term used to describe the difference between the sales price of land and the land's cost when the sales price is higher. It represents the firm's extra benefit or profit margin from the transaction.
Step-by-step explanation:
If a firm sells land for more than it costs, the difference between the sales price and the cost of the land is called producer surplus. This is an economic term that describes the extra benefit a producer receives when the market price of a good is greater than the minimum amount they are willing to accept for it. In essence, this surplus acts as the profit margin for the firm when the market price exceeds the average cost of production or procurement.