Taking this back to buying experiences. IMO, there is basic expenses like buying gas or shampoo which don’t cheapen things. But the further extremes you go like plastic surgery or renting out a hotel not just a room you’re inherently worse off.
Plastic surgery might help someone with a physical deformity, and renting out a hotel might be a necessity for a scientific conference.
You can't judge the value of a dollar based on the assumption that there exists an average person that spends it. For every frivolous act of spending you can conceive of, I can respond with a similar 'well intentioned / ethically sanctioned' act of spending, from a perspective you might not have been aware of, given you likely don't have perfect information about the state of everything in existence.
It depends on who you think you are to judge how another person lives their life. What you consider essential and what you can live without is not the absolute for everyone.
Specifics are necessary because it can determine whether something is a fundamental property of a thing, how it influences the definition of a thing, how that definition influences the perception of a thing, and the relationships that thing has with other things.
A heuristic requires specifics to be defined, in order for it's definition to exist.
What we want the heuristic for is the average case that you dismissed, which covers the majority of us. There is indeed a thing as a large majority with mostly similar experiences and status, not just an collection of unique snowflakes.
PS: Sure, perhaps their not measuring 'happiness' and if it makes you feel better call it fruitkerfluffle if you want. However, that does not invalidate the question.