One possibility is that remote developers are just more productive (or if you prefer, more productive developers are more able to negotiate a remote working all

One possibility is that remote developers are just more productive (or if you prefer, more productive developers are more able to negotiate a remote working allowance from their employer). In standard economic theory, the equilibrium wage is at the workers marginal revenue product (or the marginal revenue that their work produces for the organization). So you would expect remote workers to either earn more because they are more productive or, if remote work makes you more productive, to earn more as a result of working remotely and being more productive