I forget what the exact figure is but research suggests there is a point at which more money does not bring more happiness. In fact, as I recall, people kind of return to their personal baseline of happiness irregardless of how much money they have. I think this is true, from my own experience anyway. Money brings security and freedom to do things, but I wouldn't say I was any happier now than when we lived in a smaller house, had an older car, and so on. Whether that's because age brings other challenges or because I'm not that interested in buying luxury stuff, I'm not sure.
Edit: It's an income of $100k. After this point your happiness doesn't increase...