The board of supervisors may make the principal and interest of the bonds payable at the office of the treasurer of the county, or at any other place within the United States, including any office of a trustee or paying agent, which the board may designate, or at the office of the county treasurer, or at any other designated place at the option of the bondholder. The place of payment shall be specified in the bonds. The expense of paying the bonds elsewhere than at the office of the treasurer shall be a proper charge against the district to be paid out of the tax levied and collected for the payment of the bonds.