Their example is bad because they used a different country, if you want US wages live in the US.
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.
