Salaries of magistrates and any other personnel in the office of the magistrate shall be fixed by the Executive Secretary of the Supreme Court. Such salaries shall be fixed by the Executive Secretary at least annually at such time as he deems proper and as soon as practicable thereafter certified to the Comptroller. In determining the salary of any magistrate, the Executive Secretary shall consider the work load of and territory and population served by the magistrate and such other factors he deems relevant. The governing body of any county or city may add to the fixed compensation of magistrates such amount as the governing body may appropriate with the total amount not to exceed 50 percent of the amount paid by the Commonwealth to magistrates provided such additional compensation was in effect on June 30, 2008, for such magistrates and any magistrate receiving such additional compensation continues in office without a break in service. However, the total amount of additional compensation may not be increased after June 30, 2008. No additional amount paid by a local governing body shall be chargeable to the Executive Secretary of the Supreme Court, nor shall it remove or supersede any authority, control or supervision of the Executive Secretary or Committee on District Courts.