Money itself doesn't make people happy. I think not having to worry about how you are going to pay that bill, or where the money for the next meal is coming from does. Add that to the freedom money gives people, and it is no wonder that money seems to make people happy. The downside to that is that as humans are naturally quite cynical, having a lot of money can mean that it casts doubts on the validity of all relationships... "Do they like me or my wallet?!"