Section 3-309. Audit and payment of county charges and expenses

All county
  charges and expenses and salaries of county officers in the counties  of
  the  city  and each of them shall be audited by the comptroller and paid
  out of the fund or appropriation applicable thereto, and  the  audit  of
  the  comptroller in respect to such charges and expenses shall extend to
  the reasonableness thereof and shall, in all respects, be  as  full  and
  complete as the audit of city charges and expenses.