If I am a CEO of a remote-first company and it truly doesn't matter for me where the employees are located it makes no sense to overpay for labor in high cost of living area.
So if there's a company A that pays $X in high COL area, and $X/3 in a low COL area. And then there's a company B that pays $X/2 everywhere. Then people from the low COL area would go to the company B, and people from the high COL area would go to the company A. As a result, company B gets the same results 2 times cheaper.
Repeat this process enough times and the salaries will be equalized. Of course it's not immediate, there are companies rigidly set in their ways; there are people who won't move no matter what; there is limited supply of both companies and workers; etc, etc. But eventually the market forces will do their thing.