People seem to actually believe that 5 thousand a year gives you a middle class lifestyle in the third world. The cost of eating only rice and beans and living in a tin shack with dirt floors is pretty much the same everywhere.
I agree with your premise in general though, because given a similar lifestyle and similar percentage of savings (let's say 10%) from your salary you get in a high COL place vs. low COL place, high COL place would be more preferable, as that 10% will be higher in absolute dollar value, and a lot of goods are priced the same everywhere.
By your definition no American is a member of the global lower class, as defined purely on an income basis. That's a fine point to make if the discussion was about global poverty, but that's clearly not what this discussion is about. In effect, your comment amounts to whataboutism.
Which makes it all the more suitable for a discussion on HN, wouldn't you say?