eli5 Why do humans love to feel that they “got a deal “on something?

Question

Whats the psychology behind this

In: 3

Answer 1

Me: “I paid $10 for this.”
Other person: “Really? I paid $20.”

Now I know that there’s $10 in my pocket that I *could* have had to spend on the thing, but instead it’s still in my pocket. That’s a better position to be in.