The high price of land in metropolitan areas has implications for the efficient employment of resources. For example, in New York City, as in many large cities, sidewalk vending carts sell everything from hot dogs to ice cream. Why are these carts so popular, with over 3,000 in New York City alone? Consider the resources used to supply hot dogs: land, labor, capital, entrepreneurial ability, plus intermediate goods such as hot dogs, buns, and other ingredients. Which of these do you suppose is most expensive in New York City? Retail space along Madison Avenue rents for an average of $550 a year per square foot. Because operating a hot dog cart requires about 4 square yards, it could cost as much as $20,000 a year to rent that much commercial space. Aside from the necessary public permits, however, space on the public sidewalk is free to vendors. Profit-maximizing street vendors substitute public sidewalks for costly commercial space.