Although I'd have to poke around for the specific sources, I've read papers that showed that, in fact, subjective well-being increases continuously with wealth (per capita GDP). However, the increase is not linear, but rather logistic--which makes intuitive sense, since a $5,000 pay raise for an employee making $25,000 a year isn't the same as for one making $100,000. On the other hand, I've also read that the increase in wealth past the much-referenced $75,000 level doesn't significantly increase emotional well-being (unconscious positive/negative feelings).