It may look reasonable from your viewpoint, but imagine applying the same logic across the board: my parents are retired and get their pension from their former

It may look reasonable from your viewpoint, but imagine applying the same logic across the board: my parents are retired and get their pension from their former job in the city, but they moved to the country side. Should they get their pension slashed because living costs is now lower to them ? Or try applying that at a micro level, and renegotiate your salary every time you move in a city because your rent has changed, or you finished paying your mortgage. Your living costs shouldn't matter to your company or people who own you money in general.