It's a sure thing for some time that the carrot and the stick strategy is not working anymore. After a certain level, having more money will mean nothing, just a boost of hormones and then back to the normal life. How much is that level, this could depend. But that would be the first thing people should do when thinking about money as they are not a scope in itself...or it should't be.
I knew the researches, we are fascinating living creatures and irrational behaviour is what we are pretty good at.