Please don't see this as a lack of empathy, but I think the only solution under your control is to apply to other positions and leave when you get a better one.

And if you apply to many and can't find a better one, then try to see it as 'they pay me better than anyone else' rather than they pay me less than others in the company.

I believe (but have no evidence) that smart companies will minimize the location differences to get better talent and will get a competitive advantage, but you may need to search ...