Value-added actually does depend on where you are: in-person interactions are significantly more valuable than remote ones. Network effects from who you know (which generally depends on where you are) matter. Interactions with creative people work as sounding boards for ideas.

This is precisely why technology companies cluster in hubs - not just SV but Austin, Denver/Boulder, Seattle, etc. and aren't more or less evenly distributed.

That aside, salary is determined by supply and demand, not solely by value-added. Value-added is a factor in labour demand, but it can be totally swamped by other factors.