I am not an economist, but it sounds like you're getting at something similar to the diminishing marginal utility of money. I can't find a good source online th

I am not an economist, but it sounds like you're getting at something similar to the diminishing marginal utility of money. I can't find a good source online that explains this, but the basic idea is that the more money someone has, the less each additional increment is actually worth. For example, a $10,000 raise is a lot more useful to a person that makes $50,000 a year than to one who makes $500,000 a year. There may be a connection with progressive taxation, in the sense that if money has diminishing marginal utility, then a flat tax on money is actually regressive in terms of utility. So then a progressive tax on money is closer to being "fair" in the sense of being a flatter tax on utility.