Marginalism

Marginalism is the idea that the value or usefulness of something gets smaller as we have more and more of it. Think about candy, if you only have one piece, it's very valuable to you and you might enjoy it a lot. But if you have 10 pieces of candy, the value of each individual piece goes down and you might not enjoy each piece as much. This concept affects how we make choices about what we want and need, and how much we are willing to pay for something based on how much we already have.