The employer is paying the SV premium because either they want the employee physically in SV for job duty reasons, or because other SV companies do, so if you'r

The employer is paying the SV premium because either they want the employee physically in SV for job duty reasons, or because other SV companies do, so if you're not in SV then fewer employers are trying to hire you for SV salaries, which reduces your salary offers. If they truly don't care then why not hire two equally good people in Warsaw? It's because they do care. SV employees do not want all remote to be equal. They would very much be on the losing side of that bargain.