Each of the coroners hereafter elected in any county coming within the provisions of this act, shall hereafter receive in full payment of his services as such, such sum as the board of supervisors of such counties shall determine, which sum shall not be less than $7,500.00 per year, the same to be paid as the salaries of the other officers within and for said counties: Provided, however, That in counties having a population of 250,000 inhabitants and upwards, but not exceeding 500,000, each coroner so elected shall receive in full payment of his services as such, such sum as the board of supervisors of such county shall determine, which sum shall not be less than $2,000.00 per year.