The proceeds from the sale of the bonds authorized by RCW 47.10.790 shall be deposited in the motor vehicle fund and such proceeds shall be available only for the purposes enumerated in RCW 47.10.790, for the payment of bond anticipation notes, if any, and for the payment of the expense incurred in the drafting, printing, issuance, and sale of such bonds. The costs of obtaining insurance, letters of credit, or other credit enhancement devices with respect to the bonds shall be considered to be expenses incurred in the issuance and sale of the bonds.