A Starbucks barista in SF gets paid one and half times that in Oklahoma. They do equal work, just different locations. A lady in the Zara sweatshops in Bangladesh gets paid a dollar for the entire day, while a lady in a luxury boutique in LA probably earns 100x that. They do the same jobs, why don't we all globally decide the pay in a single currency?
Simple answer: economics. Adjusting for COL was always a thing, moving away from a high COL area always meant a pay cut. Similarly anyone who moved from India or China or Europe to the Bay, got a pay hike. And the reason this happens is supply and demand. Some people are valuable enough to companies that regardless of where they live they get the same money. Bezos or Musk can move to Madagascar for all they care. For 99.999999999% of the rest, we are replaceable. If you're gonna move to Indiana and demand Bay Area salaries, there'll be plenty of people there who can do your job for less with the same set of skills. And if not in Indiana, somewhere else, maybe India. Economics. Simple. Otherwise, we'd all be drinking $200 coffees and $500 avocado toasts.