J suspect that ceteris paribus, being frugal reduces happiness - by definition, it's not getting things you want to get.
Once you can afford something that was way out of reach before, you buy it and after the first few moments you realize it is not as great as you expected. Do this a few times, and you'll learn what is important. The more wealthy people I know do have a slightly above average car and house, but IME the biggest difference is that they have far more extreme - both in amount and in price - experiences, i.e. weekend trips, fine wining and dining etc.
Higher earners tend to just upgrade and spend more (apartment, clothes, restaurants, hotels etc), and aren't really living that differently - that lifestyle can certainly soak up maximum income achievable in a salaried job.
I think this is what the article inadvertently pointed to, that the higher salaries could lead to a sense of frustration that nothing really changed.
The next level above financial independence is financial freedom (you can just get whatever you want, from shoes to houses) - off the top of my head I would guess this is probably around the 0.01%, which would be about 32k people in the USA. As an example of freedom, these people can buy nationality and avoid immigration limitations (going rate is ~$1-5m).
The article is way off just comparing salaries. There are 3 social classes in terms of having a meaningful lifestyle distinction - those who have to work for someone else, those who don't, and those who have full freedom to decide where they go and what they do each day. All they did was compare a bunch of people in the same social class (somewhat shockingly the Romans considered this equivalent to a slave class).