I've seen this research before, but I'm always happy to be reminded of this fact – comfortable people are more happy than poor people, but happy factor levels off at $75,000. From the New York Times:

The catch is that additional income doesn’t buy us any additional happiness on a typical day once we reach that comfortable standard. The magic number that defines this “comfortable standard” varies across individuals and countries, but in the United States, it seems to fall somewhere around $75,000. Using Gallup data collected from almost half a million Americans, researchers at Princeton found that higher household incomes were associated with better moods on a daily basis — but the beneficial effects of money tapered off entirely after the $75,000 mark.

Of course, reality is more complicated than that. I've meant people who make over $200,000, but are in severe financial straights (like, the electricity getting turned off sort of straights), because of the inability to handle their money.