Suppose Trent decides to join the Photography Club. Which result would be a cost?

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