Money can't buy happiness.

Some of the happiest children I've ever seen were dirt poor in a third world country, playing games barefoot and outdoors with an empty soup can.

And then they go home and there's nothing to eat, and they're not so happy anymore.
Kids are happy when they're playing, but not when they're hungry or cold or in pain for lack of money.

Money buys you freedom from these very basic causes of unhappiness. It can't cure loneliness (although it can provide you with the means to communicate or travel so you can find like-minded people) or boredom (although it can provide you with a multitude of distractions to fill your time with). As I said, it's not sufficient for happiness. But it's definitely necessary, to a certain degree.