Having grown up poor, and now being fortunate enough to have a comfortable income, I can assure you that money can absolutely buy happiness. It may not buy you love, it may not buy you a sense of zen and personal enlightenment or fulfilment, but it can definitely increase your good:bad day ratio and how often you laugh, smile, etc.
When people say otherwise, I often wonder if they know what it's like to not have money. Quite simply, it's not terribly fun. Now, I can always afford a decent meal, I get to go on fun and exciting holidays, I get to go to the theatre and concerts all the time, I can afford as many video games as my heart desires, I get to live in safe and decidedly non-dodgy neighbourhood, I can pay all my bills and basically live a debt-free existence, and so on. Contrasted to having to eat top ramen, worrying if there's enough money to cover the power bill, hearing gunshots at night, and having free TV as the main source of entertainment, I'm far, far happier. Anyone would be, I think.
As the article points out, there may be diminishing (or negative) returns and, perhaps, the middle-class is the best off, but they are demonstratively happier, clearly...
