I don't think anyone contests the fact that money increases happiness _up to a point_. Once you have full financial security though, it becomes quite nonlinear. Outside of bonkers areas, 1 million NW gets you retirement. 10 million NW gets you that plus... toys. It's a major reason why taxation should focus on the rich (as opposed to the 'well off' e.g. high incomes). They really will not notice it aside from ideolog…
Are you speaking from personal experience or is this just what you've heard elsewhere? I've still not reached the point where more money hasn't increased my happiness, however I'm definitely making far more than an above-average wage in London. I think a great number of people could be happier with more money assuming they have good ideas on how they can spend their money to improve their lives.
The step change for me was financial independence.
It's not about income, but wealth.
A basic example - the difference between a 50K a year job and a 200K a year job is enormous if you have no wealth.
If you are FI, then other factors like the nature of the work, the hours, the location and so on are far more important.
Because once you're there, it becomes clear that money has far less value than time - you only need enough of it to do the things you want to do (of course, if the things you want to do require a lot of money, that's a possible case...)