Let me start by saying that although I work in academia in a field where I work with these issues from time to time, I am by no mean an expert in any sense of the word, although I do work with people who are - but in those cases I just do what they say, we're not 'equals' or anything. I'm just saying: I'm not arguing from authority here, no do I want to give off that impression.
The link to the original source in your link is dead, so I'm not quite sure which paper they're talking about, but it sounds like the conclusions in the 'third phase' that I described. Issues are obviously much more complex than just 'make 1000 USD more to feel a lot happier', but I'd be surprised if the study would find a real plateau after 75K, rather than a tapered off increase per dollar amount. Some studies have plots that show relationships on a logarithmic scale (after a 'baseline' cutoff point, e.g. 30k or 50k), making it much move obvious that there is a continually rising correlation (or, to put it more bluntly, that yes, more money does make you 'happier', for certain definitions of 'happy'). Of course there are all sorts of methodological issues at that point, comparing between regions, across cultures, etc etc.
Let me put it this way. There are studies who conclude that e.g. people who own 5 million are happier than those who own 100k. This is easily explained: 5 million makes you 'independently wealthy', taking away the stress from having to hold a job to provide subsistence. Do people who make 75k a year typically have 5 million? No. Would it be reasonable to assume that somebody making top 1% in a community would have the same level of happiness than somebody else in that same community who makes double? Yes. So it's all in what you measure and compare. I'm sure the authors of the article referenced in your link acknowledge that, but that they just had a much more narrow research question; a question that lead to the magic number of 75k within the confines of their research. Those nuances get lost in the AP summary, then again in the WSJ summary, then even worse in the headline. I mean the WSJ blurb even acknowledges that happiness does continue to rise even after 75k.
I'm not sure where I'm going with this, just that your link does describe an increasing effect after 75k and not a 'hard' plateau, so yes it's consistent with what I posted before.