I think you'll find that remote developers' salaries vary as much as any other worker. I work remotely for a company based in NYC. My employer based their initial offer on the average salary for software developers in the city that I lived in at the time. I countered for much higher ($135k) and got it. Now I live in San Diego, which has one of the highest costs of living, but I feel the tradeoff is worth it.

This company also hires lots of developers from around the world, in places with much lower cost of living and I suspect their salaries balance out, so to speak, with mine and the local NYC employees.