Suppose Destiny decides to watch the action movie. Which result would be a cost?
Destiny will give up the chance to watch the movie that she is more excited about. Destiny will get to watch a movie with her sister.
Destiny 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. Destiny'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 Destiny wants or needs:
Destiny will give up the chance to watch the movie that she is more excited about.