Decreasing marginal utility of money is just a theory, and there are many flaws in the theory - including measuring happiness with a discrete scale of questiona

Decreasing marginal utility of money is just a theory, and there are many flaws in the theory - including measuring happiness with a discrete scale of questionable boundaries (5=very happy, etc.), considering self administered questions at face value, etc. Another theory is hedonic adaptation- you adapt to whatever and regress to a baseline. Finally, there seems to be proof that some people do not spent their money on what will make them happier, the typical example being buying an object instead of an experience.