Suppose Colin decides to go as a superhero. Which result would be a cost?
Colin will save some time and money. He won't have to go out and get a new costume. Colin will give up the chance to wear the costume he is more excited about.
Colin is deciding whether to go as a vampire or a superhero to a costume party. He would rather go as a vampire. But he already has a superhero costume.
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 Colin wants or needs:
Colin will give up the chance to wear the costume he is more excited about.