If the estimate of the board is not agreed to by the owner or keeper of the bridge or ferry, it shall be fixed by three commissioners, one to be appointed by the board, one by the owner and keeper, and the third by the presiding judge of the superior court, who shall hear testimony and fix the value and cost according to the facts, and report it to the board of supervisors under oath. In all estimates of the fair cash value of the bridge or ferry the value of the franchise shall not be taken into consideration.