Nobel Prize-winning economists Angus Deaton and Danny Kahneman at Princeton University published a study a few years back and came up with a figure of $75,000 USD/annum as the point at which happiness peaks. But "satisfaction" is a slightly different metric, more related to long-term goals and not day-to-day "happiness." (May need to adjust for inflation since 2010 and variability in cost-of-living worldwide.)