When I was a teacher, earning a low salary (even by teacher standards), I still had over $10k of disposable income. I can't imagine that'd go down at all if my salary tripled or quadrupled (thereby bringing it into the range he discusses).
I'm presenting what happens by default in both options, not one optimized and one non-optimized option. What you discovered here is that, the plan to save money in the outback is robust and succeeds by default, while the plan to save money in the US is fragile and fails by default.
For instance, the US rationalist has an easy solution to the keeping-up-with-the-Joneses problem: Don't. I've had great success with this. It's not that hard. While there is always a dick waving contest going on somewhere in a neighborhood it's really quite easy to opt out, and for the most part nobody comes and chases you down; the dick wavers simply classify you as a loser and you decline to correct them. QED.
That whole post is rationalist fail; he knows the forms, but he isn't dancing the dance. It isn't just another brand of marketing to slather over your preexisting point or desire. Well, actually it can be used that way just like any other good thing and this is far from the first self-proclaimed rationalist I've seen to fall into this trap, but hey, we all do it somewhere. We're all still human, no matter how hard we try.
I view his plan as being similar to not purchasing ice cream while you are dieting - if you were perfectly rational, you could rationally choose not to eat the ice cream in your freezer, but why give yourself the temptation to be irrational?
... still, I really do find it hard to believe that you are so weak willed that you would do such a non-optimal thing, but you are willing to fly all the way around the world, where, I might add, such temptations will still be present even if they aren't quite as pressing. This whole argument, if it's going to apply to anybody, sure strikes me as sailing through a narrow window at best, while proclaiming the window to be far larger than it actually is.
If the Millionaire Next Store is correct, you're likely to spend more if you live in a nice neighborhood (keeping up with the Joneses).
I notice this myself. A coworker who lives in very nice neighborhood has a BMW. I drive a 14 yead old vehicle and live in a "down scale" neighborhood. So our roughly equivalent salary is going to seem much different to him (money is tight) vs me (lots of disposable income).