that depends on what happiness means for you, and weather you believe that such a thing really can last.
i think that happiness is momentary and vision based, so depending on what you need for being happy it's possible to buy happiness.
in any case, it eases things much, but that doesnt mean that everyone with money who wants to be happy can simply buy it.
when i drive with 120 miles/h, i am happy, but you need money to drive fast, because the police dislikes it, it consumes much more fuel and your car has to be able to drive fast.