In my opinion money can't buy happiness but it can help you clear the way for you to find what makes you happy. And if used only when needed It can greatly reduce stress from worring about if you can afford things that you need and even little things the you want. In short: it cant buy you happiness but it can pay off saddness and stress if used correctly.
Actually, if you want to get into the chemistry of it, happiness is induced by a hormone in your brain known as dopamine. Certain things can spark the dopamine reactors. One of these things, is, unsurprisingly chocolate. Chocolate has a lot of surprising health benefits in moderation, but I won't go into that right now. Another thing that involves dopamine is cocaine - it blocks the dopamine receptors so that you're getting a constant dose of happy. Speaking of cocaine, has anyone else realized that pure caffeine looks EXACTLY like powdered cocaine? Wonder if they work on the same principle... To the interwebz!