Money has diminishing returns upon happiness, nonetheless, a certain amount of money is necessary for people to be happy because practically all people need it to have the material preconditions for happiness. Beyond that threshold, however, money only has value as a relative good, for generating a feeling of "doing better" than others, and does not add to the overall happiness of the society. See wiki:

Typically market health measures such as GDP and GNP have been used as a measure of successful policy. However, although on average richer nations tend to be happier than poorer nations, beyond an average GDP/capita of about $15,000 (most of the world's nations have less than this), studies indicate the average income in a nation makes little difference to the average self-reported happiness.

The world has an average GDP/capita of $10.200 (PPP, according to the CIA World Factbook), so we will still need some economic growth to satisfy the needs of all.