Suppose Eva decides to plant the tulips. Which result would be a cost?
She will save some space. The tulips will use up less space than the hickory tree would have used up. Eva will give up the chance to look at the hickory tree. She thinks it would have looked more beautiful than the tulips.
Eva is deciding whether to plant tulips or a hickory tree in her backyard. She wants to make her backyard more beautiful. But she also wants to leave space for doing fun things.
Before you decide to do something, it is often helpful to list costs and benefits.
Costs are what you give up or spend when you decide to do something. Costs involve giving up things that you want or need.
Benefits are what you gain or save when you decide to do something. Benefits involve gaining something that you want or need.
This result is a cost. It involves giving up or spending something that Eva wants or needs:
Eva will give up the chance to look at the hickory tree. She thinks it would have looked more beautiful than the tulips.