Suppose Vincent decides to plant the poppies. Which result would be a cost?
A: Vincent will give up the chance to look at the eucalyptus tree. He thinks it would have looked more beautiful than the poppies.
B: He will save some space. The poppies will use up less space than the eucalyptus tree would have used up.
This result is a cost. It involves giving up or spending something that Vincent wants or needs:
Vincent will give up the chance to look at the eucalyptus tree. He thinks it would have looked more beautiful than the poppies.