Suppose Nancy decides to watch the comedy. Which result would be a cost?
Nancy will get to watch the movie that she is more excited about. Nancy will give up the chance to watch a movie with her sister.
Nancy is deciding whether to watch a comedy or an action movie. She would prefer to watch a comedy. But she also wants to watch a movie with her sister. Nancy's sister will only watch an action movie.
Before you decide to do something, it is often helpful to list costs and benefits.
Costs are what you give up or spend when you decide to do something. Costs involve giving up things that you want or need.
Benefits are what you gain or save when you decide to do something. Benefits involve gaining something that you want or need.
This result is a cost. It involves giving up or spending something that Nancy wants or needs:
Nancy will give up the chance to watch a movie with her sister.