You may be interested in this newer paper, reconciling the work of Killingsworth and Kahneman & Deaton. https://www.pnas.org/doi/10.1073/pnas.2208661120
Whether it's a straight line up to $75K followed by a flat line from there on, or a curved (log) relationship all the way up, seems to me to make rather little difference.
Would “Income and emotional well-being: It doesn’t really matter” be a better title for the study? Or do I miss something?