Fair, but I actually enjoy my work (one of the things I feel like I have gained by avoiding FAANG), so retiring at 40 doesn't have that much appeal.

That's a quite an interesting paper! That said, the final results still line up with my intuition, which is that there are diminishing returns, as evidenced by the log(income) relationship that that new study identifies.

I already make a 90th percentile income for my area, and I don't feel that investing additional mental and emotional resources in maximizing salary is the best route forward for pursuing happiness. I think that at this point there are other axes to optimize on that provide greater marginal gains to happiness.

A big issue with any analysis of happiness is that it's rated on a "capped" scale. For example they ask you "how happy are you 1-10". However income is "uncapped". That means there will always inherently be a sublinear relationship between the two in any analysis, because you are compressing the top end of happiness.

I think for most people amounts up to something like 200-500k/yr (depending on COL) would provide increased happiness. Basically, if you ever have to worry about not having enough money, you could stand to make more.

Of course that doesn't mean it's necessarily worthwhile to work more to achieve that, that would be a personal decision you have to make yourself.