One thing I would like to add is that I think it is plausible that the results might not be even close to the same if Killingsworth's study contained responses from folks living in low-income countries. For example, I wouldn't be surprised if money actually has a much stronger effect on happiness for people earning $500 ~ per year, as things like medicine, food, shelter, sanitation, etc probably bring significantly more happiness than the kinds of things bought by people that earn $400,000+ per year.
Also, even if it does make a small difference (which I find hard to believe at such a low income), you can double, triple, quadruple, etc the income of 100 people earning $500 per year for a lower cost than doubling the income of one person earning $200,000.
Since we can't directly prove this from Killingsworth's study — which the blogpost was primarily about — the assumption was that the results would be the same for low-income earners.
Thanks for the kind words Linch! Yes, I agree with the motivated reasoning point. I found myself pretty attached to the $75,000 anecdote (me being a fanboy for Kahneman probably contributed to this) even though it didn't feel quite right. Glad that this new paper allowed me to update while still aligning with one of my core beliefs.
I think Killingsworth's study captures the same idea that motivates me to do the GWWC pledge while being a bit more nuanced than Kahneman & Deaton's study. I really do hope this new research can enrich the EA community's view on the relationship between money and happiness.