People have a sort of natural baseline level of happiness, different for each person. When bad or good things happen you move the needle a bit, but when you get into a steady state it moves right back to your baseline. Unless you live in a situation of genuine poverty it's highly unlikely that having more money will make you happier. I know all sorts of income classes and i don't know of a difference in self-perceived happiness among those classes. You can mock rich people for the silly worries they have (like how best to invest their money) but that doesn't mean those worries aren't just as real to them.

(Incidentally, the book The Happiness Hypothesis covers this subject as well as how to actually become happier.)