You CAN buy Happyness!!!
In biology, the brain works using something called neurotransmitters, which are released upon certain stimuli from the 'real' world via your senses. e.g. You look at the sun setting, it triggers memories, and you smile.
It so happens that there are certain chemical neurotransmitters called Endorphins, which, when you are stimulated in a certain way, result in you feeling happy. (There was also a report about chocolate having similar effects...)
So that means...
If you could somehow get hold of endorphins, either ingested (eaten), injected or whatever...
Then you CAN actually buy happyness!!!
PS.... I noticed this idea is pretty similar to that episode of Doctor Who (Gridlock, for those of you who want to look it up :) where they were selling drugs in green packets in the stalls...
PPS... Somebody sparked up that the EVIL drug heroin has a similar purpose... however, heroin is made from morphine, and is highly addictive, so I DO NOT suggest you ever, ever, ever take it!!! Ever!
(Not that I'm forcing you to become StraightEdge, as your life is your own choice of course!)
But the great thing about this whole idea is that endorphins are already made by the body itself - they are naturally-occurring chemicals - in fact, if you didn't have any, you wouldn't be human!!!
In effect, you are therefore bypassing the whole neurotransmitter-release stages that heroin has to go through in order to make you feel happy - endorphins are just the end result of taking heroin! (Well what I am led to believe anyway).
All I'm saying is, happyness is just a state of mind, caused by chemicals in the brain. If we could reproduce these chemicals and get them into the brain... then it would be true that you can buy happyness :)