Is there an economic term that means the same thing as "personal inflation"

Question

I don't have anything even close to what would be considered formal education in terms of economics, so the term "personal inflation," is just something I completely made up. What I mean by personal inflation is that, in terms of living condition, 1000$$ given to someone who is already a millionaire isn't going to be worth very much because, compared to the amount of money that person already had before, 1000$ isn't very much money. However, if that same 1000$ were to be given to someone who had little to no money, the money would be valued at much more and raise the living condition, for at least a little while, of that person much more than it would the millionaire.

What my questions is regarding is what the better term for this "definition" that is explained above is, and/or whether there are terms the fit this description above fairly well, but are slightly different.

Answer 1

What you describe is called "decreasing marginal utility of income". Marginal utility is just an economist's way of saying the benefit you got out of the last unit of something, and decreasing because we think this might be lower at higher levels of income.