All of your examples are geography dependent and is not actually equal work - the Oklahoma barista can't do the same job as the SF barista, because telecommuting baristas is not a thing.

But if the job role is to maintain a server fleet, and you can realistically do the job from anywhere, then you should get paid the same amount whether you happen to be in SF or Oklahoma, since you can complete the job in the same manner.

Equal pay for equal work makes sense - what doesn't make sense is to assume that the pay will normalize into bay-area level pay, versus bay-area level pay being lowered because companies realize they can pay everyone 70% as much and have the employees live in lower cost of living areas.