If money doesn't buy you happiness, you don't have enough money.

For example, what would you do if you had ten billion dollars ? Some people would answer, "I'd buy my own zoo !" or whatever, but the real answer is, "I would never work again; instead, I'd pursue whatever projects I found interesting“. That kind of freedom could enable you to be quite happy.

I'm not sure if this kind of experience scales to lower amounts of money; there's probably a minimum threshold above which wealth becomes entirely self-sustaining, and below which you'd still have to work for a living. Still, even below the threshold, you can still spend your money on automating and outsourcing smaller chunks of your daily drudgery, thus indirectly purchasing happiness.