... A, for example, must pay $100 to eliminate the first unit of sulfur dioxide and $200 to eliminate the second. Firm B must pay $200 for the first unit and $600 for the second. Although the information ... people pay for them every year shows that there is a demand, illustrated by curve D1 in Figure 7.3. In getting shots for themselves, however, people also provide external benefits for others. ... without paying for its use. Costs that are not borne by users, of course, are passed on to others as external costs. When public land was open to grazing in the West 150 years ago, for instance,...