Salary[; members of advisory board].

In addition to salaries received as elective county officers, each member of a county advisory board, except the county commissioners, shall receive six hundred dollars ($600) a year, plus three hundred dollars ($300) additional for deputies. Each county commissioner shall receive three hundred dollars ($300) a year; provided, that only so much of the salaries of each member of the board shall be allowed as the county's valuation will raise for the salary funds within the twenty mill limitation.