Perhaps I'm missing your point, but it'd be strange if there were no consensus on what is a straight-forward matter of fact. There might be dispute as to _why_ they are paid less -- issues of productivity, whether the work is equivalent, etc. -- and one can argue as to whether they should be paid the same, and what is the political significance of the difference, and so on. But being paid less, whether converted at exchange rate or at PPP, is not, I think, in doubt.
Take, for instance, assembly-line work in Intel. As far as I can tell, levels of productivity in production of CPU's, e.g., are not any lower in Penang, Malaysia, than in the US. But even if they were 50% lower, wages are definitely more than 50% below that of the US. And Penang, Malaysia, would be one of the higher wage areas outside the US.
kj khoo