Example you work for NewYork/SanFrancisco/etc company and live in Italy. You make $80K and save half of that. Depending on how good you are as a developer + finding better clients you can live in a cheaper country, say Bulgaria/Albania/etc and make more than 80K+(ex Salvatore Sanfilipo though he's special). Usually the more you get paid by the clients, the better they treat you as a human/professional. The clients who will pay you the most, are the ones that pay the most local-salaries, which is Sf,Ny,Washington etc, major us-cities. Maybe London a little too, but probably not (I don't know london having 150K salaries locally?).