The U.S. government bought 112,000 acres of land in southeastern Colorado in 1968 for $17,500,000. The cost of using this land today exclusively for the reintroduction of the black-tailed prairie dog is zero, because they already own the land. is zero, because the land represents a sunk cost. is $17,500,000 is equal to the total dollar value the land would yield if used for farming and ranching.