Another argument for globally similar rates could be that cost of living is also to some degree a reflection of additional value (high quality education and healthcare, safety, etc...) which individuals in low income locations may lack. Getting paid the higher rate is a form of compensation.

However, I haven’t seen the same argument for other salaries. What makes a developer different from a musician, a lawyer, an architect? Or, for that matter, from a teacher, a waiter, and a bus driver? Shouldn’t the same argument that the work is the same apply?