Suppose Shelby decides to eat the sugar cookies. Which result would be a cost?

 - Shelby will get to eat the sugar cookies. Shelby thinks sugar cookies will taste better than grapes would have.
 - Shelby will give up the chance to eat the grapes. The grapes would have been healthier than the sugar cookies.
This result is a cost. It involves giving up or spending something that Shelby wants or needs:
Shelby will give up the chance to eat the grapes. The grapes would have been healthier than the sugar cookies.