@Qazwer I'm thrilled that the work I did has been useful to some folks. I spent a lot of hours thinking about the post before I ended up posting it. You've not spent that sort of time and so I don't expect off the cuff responses to be as thought out. I don't take any offense, it is hard to discuss an abstract topic, judge one group (average Americans/Westerners) against a single "idealized" individual and not sound judgy somewhere in that, be it the creator of the measure, the idealizing, the individual or the average group. It is at least part of why academics end up sounding like they are in ivory towers. Hopefully I'm not sounding like a dismissive academic jerk either in my phrasing, I'm going to assume you try to read this with best of intentions.
My very small effort just asked, WWJD, what would average joe do and what big differences in outcome make themselves obvious. Of course with only 20 items it is probably not statistically sound, but this isn't the only data point we have. We also have Jacob's actual numbers, Jacob's own measure of reasonable expenses (using earth population), CPI itself, average consumer behaviors and I certainly personal looked at way more data points than I captured. I think leaving the breadcrumbs and a methodology which allows anyone else to build up a intuition about my theory. I started this project asking "Is CPI reasonably sound?" With a lot of examination, reading way more than I linked to and a lot of thinking, I think "near enough" is about all one needs to know, unless it is personally of interest (like us money-nerds find it).
However, a new question showed up, unexpectedly. In a sense I'm trying to ask the question, "Why does ERE work?" My intuition is that it works because the things that inflated the most are modern convinces or in ERE+economics parlance unnecessary goods while goods that ERE deems generally necessary have stayed cheap all the while wages have increased. The wage increasing is a big aspect of this and goes counter to common narrative of wages not increasing since the 70s. This does lead to the FAT/LEAN-FIRE, FIRE for professionals only style discussions. With ERE style FIRE you have a tendency to live in 1900-1960s style expenses with a few cheap perks thrown in. This means the wage increases from 1900 to 1960s are in fact part of what makes ERE work. In efforts to go through history like that cited here
it seems ERE could have started anywhere mid-century on. Of course ERE as a broad philosophy rather than a lifestyle might go back much further (e.g. Resilience, Anti-fragile), but that is not really what I was getting at. I think this gets me to about as far as I have thought this through.