> and employers believe it is fair to adjust the salary to provide a similar quality of life to both
That's bullshit. E.g. electronics cost the same in all countries.
Sure, but how much of your wage do you spend buying electronics? The vast majority of my salary goes to fixed expenses like housing, food, healthcare, energy, and transport. Those are all highly location-dependent.
In location A you might spend 80% of your salary on fixed expenses, whereas in location B you only need to spend 20% of that same salary to pay for those expenses - leaving you with far more money for discretionary spending.
Actually, no they don't. With various forms of VAT and tariffs, things definitely do not cost the same in all countries.