Seems like it is based on:
https://www.purdue.edu/newsroom/releases/2018/Q1/money-only-buys-happiness-for-a-certain-amount.html
https://www.researchgate.net/publication/321743107_Happiness_Income_Satiation_and_Turning_Points_Around_the_World
with list of cities from:
https://finance.yahoo.com/news/minimum-salary-happy-biggest-cities-100000022.html
Andrew Jebb (the lead author) said that “We found that the ideal income point is $95,000 for life evaluation and $60,000 to $75,000 for emotional well-being.” (The amount is for individuals.) Note that “life evaluation” is a lower level than what the second linked page lists to be happy. For example, that page lists $182,820-$228,525 for “emotional well-being”, $289,465 for “life evaluation”, and $319,935 to “be happy” in San Francisco. No way do any of these make sense, unless they are based on very expensive lifestyles.
According to https://dqydj.com/average-median-top-individual-income-percentiles/ , $95,000 (“life evaluation”) is about the 85th percentile; $60,000 to $75,000 (“emotional well-being”) is 68th-77th percentile.
On the other hand, if people really do feel that these income levels are “poor” (seems like a common theme on these forums where a high enough income not to get college financial aid for the kids is only “middle class”), then it is not surprising that there is so much focus on high pay jobs like investment banking, management consulting, biglaw, the highest paid physician specialties, etc… and the college paths to get to those jobs.