Suppose Joe decides to bake chocolate muffins. Which result would be a cost?

 - Joe will get to eat more muffins. He can make more chocolate muffins than pumpkin muffins.
 - Joe will give up the chance to eat pumpkin muffins. He thinks pumpkin muffins are tastier than chocolate muffins.
This result is a cost. It involves giving up or spending something that Joe wants or needs:
Joe will give up the chance to eat pumpkin muffins. He thinks pumpkin muffins are tastier than chocolate muffins.