Suppose Ernest decides to get the cake batter ice cream. Which result would be a cost?

 - Ernest will give up the chance to eat the praline pecan ice cream. He likes this flavor more than cake batter.
 - Ernest will get a free waffle cone. He will enjoy the waffle cone.
This result is a cost. It involves giving up or spending something that Ernest wants or needs:
Ernest will give up the chance to eat the praline pecan ice cream. He likes this flavor more than cake batter.