The point that grandparent and ohhhwell are making is, nobody says "I came to Japan and now my salary is 100x my previous salary in nominal terms (ie, before you factor in the exchange rate that eats 99% of your salary)". But for some reason people do say things like that when the currencies involved are USD/CAD/GBP/EUR. I guess it's just not as obviously "wrong".
Just normalize everything to a single currency; we can still talk about differences in cost of living. Sure, exchange rate fluctuations can be related to the cost of living, but it's not everything.