By location or By skill? I think equal work, equal pay. So I am in the same-work-same-pay camp. Big companies like Twitter and Facebook cut your pay if you move to a cheaper location (ugh).
Most of remote companies choose to pay based on local rates with good intentions to be truly fair: Why GitLab pays local rates and Buffer. But I think it is better to pay people for their Skills, not where they live.
If you say someone live in a 50% cheaper location in terms of cost of living. But you have to live there and that’s their choice. It is about value added from the work, not where they live!
Market rate becomes higher? Adjust yearly.
People growing too fast? Promotions.
How about your company?