I think society has changed a bit in terms of network effects and how much you had compared to a fixed group was more significant to both you and them when the original study was done.
Whether or not this idea is wrong is actually besides my point.
My point is that one of the main reasons this idea spread so quickly is because it provides comfort to those who are not wealthy.
It actually seems to say that disvomforts required to earn a lot of money would make you less happy than earning a good amount with less effort and it generally won't make up for more relevant factors in happiness. I.e. an easy tenure would make someone happier than being a law partner earning 4 times more.
But I agree with fairity that a lot of the appeal of this pop-science junk idea "$75k is all you need" was "haha, those rich people aren't actually any happier than me, in fact they're making dumb choices because more money is a dumb thing to pursue".
It's just not true. Much richer people are in fact very likely to be happier than you. Not 100% of the time, because money doesn't solve all human problems, but 10x more money solves a huge fraction of problems for basically everyone, and people who aren't rich are just fooling themselves a lot of the time.