1,50$ can make you happy when you sleep under a bridge.
10000 a month can leave you unsatisfied if you are a manager.
The question is not so much about the "how much" but about "what can you do where you are with a certain amount", the buying power and the personal values. If you can answer the question:
"define an amount of wealth that gives you happiness" they will give you immediately the Nobel in Economics. You will be amused, but when you go to University and you study what are the aims of economy then you will read that the last aim is "happiness" of the society. Now I do not know about the
how much. It is more about
what makes you happy. Some motivation like freedom money can't buy. I've seen so many male "prostitutes", manager of "high society", with more then 10000 dollars a month, much more, that where not happy at all, because they had to betray their values and they knew it.
From an economical point of view there seems to be a cut off point. At a certain amount you do not actually spend all, not even half what you earn. The money goes in savings and then in the heritage, (the one for which your wife/husband at a certain point did put the poison in your morning coffee, just to be clearer
).
Probably money makes you "happy" if you do not feel restraint in your hedonistic choices and when you do not feel too much you have to prostitute yourself every day to earn it.
Italian saying: "chi s'accontenta gode" = who is ok with what he has got, enjoys. The classical way of people to answer this is: "cosi, cosi!" = so-so!