Money can buy security and that security increases your happiness. Not having money can make you unhappy. Sustainable happiness is recognizing what is truly valuable in life and appreciating it. For me this is: 1) No debt 2) Full stomach/quenched thirst 3) A warm place to sleep 3) Meaningful intimate loving relationships 4) A sense that I am valuable (adding value to the world or some subset) 5) Freedom to indulge my…
2. Full stomach/quenched thirst is trivial if you don't mind tap water and simple starches, but once you add (depending on your taste) a complement of steak, quinoa, fresh fruits, beer and/or wine - then you run into a little money.
3. Warm place to sleep - anywhere near work? public transport? "good" schools (however you define that)? Gets expensive quick.
3bis. Meaningful intimate loving relationships are easier to maintain if you have at least one weekend day off (i.e. don't have to work 2 or more jobs) and have at least a little cash to go out on the town at least once in a while.
4. Sense that I am valuable - to me, this has always been difficult without a modestly good set of clothes, shoes and a haircut. Others don't feel that way (but less than you'd think). But maintaining a personal sense of one's value is at least somewhat correlated with others' sense of ones' value. And others' sense of one's value is never completely monetarily free.
5-6. Freedom to indulge curiosities and spiritual life - on a low income, you'd better be single and childless. And even then, it's a challenge.
I very much doubt the average person could fulfill those goals to any degree of satisfaction on less than 50k as a single person in a major metro area, not a ton less in the boondocks, and not much less than double that with a partner or spouse.