But of course, the salary of employees is not purely based on the value they provide. It's also based on availability of labor.
COVID-19 doesn't really change the equation. Remote workers are already paid based on the prevailing wages in their locality.
Someone who was working in the bay area and now has been given free rein to go permanently remote is simply new to the remote work system, and they absolutely should expect a lower wage if they decide to live elsewhere.