Firebaugh argues that, in evaluating their own incomes, individuals compare themselves to their peers of the same age. Therefore a person's reported level of happiness depends on how his or her income compares to others in the same age group. Using comparison groups on the basis of age, the researchers find evidence of both relative and absolute effects, but relative income is more important than absolute income in determining the happiness of individuals in the United States. This may result in a self-indulgent treadmill, because incomes in the United States rise over most of the adult lifespan.The research puts an interesting spin on "keeping up with the Joneses". Firebaugh tested what he calls the "hedonic treadmill hypothesis" where "keeping up" means continually increasing one's own income because you can be sure the Joneses are increasing theirs.
Also, continued income growth in wealthy countries is irrelevant to the people's happiness because it could cause a consumption race just to maintain a constant level of happiness.
I say, give me the money and let me take my chances.