But within the US it's pretty ridiculous.
Not all of how you spend your pay is scaled by your cost of living for example...
My employer can't predict where I want to retire, yet by scaling my entire pay by cost of living where I currently am they'd be limiting how much I can save.
You can live in a high cost of living area and decide you're ok with living with roommates and ramen noodles. That results in the same living expenditure as someone in a low cost of living area with significantly more room to save.