Well yes one can argue about the basket used in the referenced study. I haven't looked into which one was used exactly, but in my experience of working with UN

Well yes one can argue about the basket used in the referenced study. I haven't looked into which one was used exactly, but in my experience of working with UN data (of which the WHO is a part), their measurement methodologies are usually quite sound and well-reasoned (of course you can always find something imperfect in the margin, especially for decisions made in the past and that haven't been changed to make it possible to measure change over time, but I'm talking overall). But that's quite a difference from the claimed and unsubstantiated 'totally wrong'. For the second point, I don't think I'm fully understanding. Yes you can use exchange rates as a proxy or second-order measurement for inflation (measurement, not prediction, unless I'm missing something); but I fail to see the relevance of that for the current study, since we're (presumably, again I haven't studied the methodology and more specifically basket used to measure inflation/PPP in that much detail) talking about goods that are relatively little influenced by exchange rates (i.e., much of the consumption of the people on those 2$ budgets is local and based on subsistence farming and local trade).