Yeah I've been writing about this subject forever. But it's so rich for exploration!
Check out this chart:
Source: Betsey Stevenson and Justin Wolfers, Subjective Well‐Being and Income: Is There Any Evidence of Satiation? National Bureau of Economic Research April 16, 2013 draft
Ok, a bit old, but I doubt things have changed all that much since 2007. Bottom line: by the time you hit the median income in the US, chances are (like 91%) you are very happy or fairly happy. And the vast majority of American households will hit at least the median within their lifetimes. That's not too shabby (even though more money makes things even peachier).
I'm not one to bemoan the fact that Americans are lower on the Happiness Scale than many European countries. It may look bad when the World Happiness Index lists the US as 14th in their rankings. But the US still scores a 6.99 on the stupid scale, when the happiness winner - Norway - is just 7.54. So we're talking about a measly .5 difference from the top to the US - about the same difference as between the US and France. And the US is a huge country. Norway has a population of about 5,267,000.