The Pleasure of Being Above the Rest
I agree with Stuart's excellent observation about the weakness of the survey question. The study I read on the question of whether wealth makes people happier, however, relied upon a cross-cultural survey of people's self-reported levels of happiness that didn't suffer from this weakness. Respondents were asked to select a face that best matched their general mood; the faces ranged from full-toothed smile to desperation. Among those with at least minimum necessities, the study found that there was almost no correlation between additional wealth and the survey responses. (The reason for the fuzzy "almost no correlation" construction is because the study reported that people with more money did disproportionately choose happier faces, but the discrepency was within the margin of error.)

Laylard's idea also accords with what is probably my all-time favorite observation of C.S. Lewis. From his classic essay, The Great Sin:

We say that people are proud of being rich, or clever, or good-looking, but they are not. They are proud of being richer, or cleverer, or better looking than others. If every one else became equally rich, or clever, or good-looking there would be nothing to be proud about. It is the comparison that makes you proud, the pleasure of being above the rest.