It's even more complicated than that
It's even more complicated than what you're saying. For example, here in Canada, controllers in Gander, Newfoundland or Moncton, New Brunswick can live like kings on their ATC salary and controllers in Vancouver or Toronto can only buy a condo or row house. The salary is about the same, but the cost of living across the country can be very different.
I'm sure it's the same in other parts of the world too; Los Angeles would be much more than Salt Lake City...
If an American controller working in Gander decided to go home to Los Angeles, his pay would be more on paper, but it would feel like he took a 50% pay cut (at least). Or if I (in Vancouver) transfered to Moncton, I could have a house with a pool on the atlantic for half the cost of the my row house here!
So even if you stay in the same currency, the whole picture is still scewed - let alone switching from one currency to the next and travelling across the world.