Suppose Brianna decides to join the Theater Club. Which result would be a cost?

 - Brianna will save some time. She would have spent more time in the Photography Club than in the Theater Club.
 - Brianna will give up the chance to be in the Photography Club. She would have had more fun in the Photography Club than in the Theater Club.
This result is a cost. It involves giving up or spending something that Brianna wants or needs:
Brianna will give up the chance to be in the Photography Club. She would have had more fun in the Photography Club than in the Theater Club.