2x salary, 2x costs, 2x savings. The savings are far greater if they compound in investments, and if you're remitting income to someone who lives in the lower cost of living area, it can be worth it.
100% this. Maxing out the 401k annually at the relatively low salary of 150k in NYC is easy. Doing that in St Louis at 50k livable wage is super hard. Car payments? Ditto.
I does matter if you plan to move to a cheaper area after a retirement. Or even if you are buying a car which costs about the same from California to Virginia - only local goods/services (and housing of course) are more expensive in high cost high salary places. Everything else if about the same within a given country.