Economists factor costs in many different ways.
Though you may read the cost of a soup can at $1 as it’s listed on the grocery store shelf, economists view the cost of the soup can in very different ways. For example, an economist asks what you are giving up to buy that can of soup over another item. They measure the firm’s cost of producing that soup can as it relates to their output and factors of production. Thus, the different types of economic costs are varied.
Sunk Cost
A sunk cost is an expense that cannot be recouped. Mark Hirschy, author of the book, "Fundamentals of Managerial Economics," explains that sunk costs should not factor into a decision when deciding between alternatives. For example, say a person spent $50,000 on a degree in education and earns $60,000 as a teacher. She is later offered a job in marketing that pays her $80,000. Though she may be tempted to factor in her education degree as reason to stay in her current teaching job, her $50,000 degree is regarded as a sunk cost. She already spent this money, and it cannot be recouped. In this case, she should only compare the respective salaries of the positions. If all else is held equal, she should pursue the marketing job.
Opportunity Cost
An opportunity cost is the value of an alternative choice. Though the word "cost" usually equates to a numerical value, like a dollar figure, this is not always the case. William Baumol and Alan Blinder, authors of the book, "Economics: Principles and Policy," state that an opportunity cost calculates intangible things like time, location and job satisfaction. They explain opportunity costs are what you give up to follow one course of action. For example, a college graduate is deciding between a job as a tech consultant in Seattle or an investment broker in New York City. If the grad pursues the investment broker position, the opportunity costs of foregoing the job in Seattle could be a slower pace of life, $10,000 higher salary and lower costs of living like rent and food.
Marginal Cost
A marginal cost is the amount it takes to produce one more item. Under this view of costs, they vary along the production line and in most cases the cost to produce a good reduces over time. Intuitively, this makes sense: the more proficient you become at producing a good, the faster you can do it and less waste is produced. The savings in labor and material as you achieve "economies of scale" means the cost of production usually decreases. The way economists find the marginal cost is by taking the derivative of the total costs as it relates to the total output.
