Much of the work of product development and marketing is creating differentiation (real and perceived). Is a Mercedes E-class different from Toyota Camry? Is 90% lean ground beef from Whole Foods different from 90% at Trader Joe’s?
Is economy class 21-day advance, Saturday night stay required travel different from a walk-up ticket out Tuesday back the same Thursday?
Sure, and that's definitely an important phenomenon, but it is not really germane to hiring for a role and paying differently for the exact same role depending on where the successful applicant lives.
For this example, obviously they are different. The job of marketing is to justify the difference in price for whatever differences the Mercedes offers.
> Is economy class 21-day advance, Saturday night stay required travel different from a walk-up ticket out Tuesday back the same Thursday?
Yes, for the seller, guaranteed payment 21 days before is different than a volatile payment minutes before the goods expire.
I would say that software engineering labor is extremely differentiated?
https://www.deirdremccloskey.com/docs/price.pdf
http://www.daviddfriedman.com/Academic/Price_Theory/Price%20...
Except for differences imposed by differential transaction costs, freely competitive markets have one price for a given good. If there's not a single, global rate for a nondifferentiated good, it means it's not a competitive market and a cartel or monopolist is imposing segmentation.
If there's some places where the supply (in the economic sense of the function relating price and quantity delivered) is restricted so nothing is delivered at the global market clearing rate, then that place just isn't a source of the good.
The benefit of segmentation for buyers isn't that they get to avoid being priced out of markets where you pay more for the same service, it's that imposing segmentation lets you reduce the price you pay to suppliers in low-cost regions to a level below the global market clearing price.