The cost and expenses of work executed by the municipality itself shall be paid out of the improvement fund, but the amount appropriated and used from the fund for this purpose shall not exceed the amount of the bid upon which the award of the contract was made, or if no bids are received or the work is ordered without asking for bids, the cost and expenses shall not exceed the amount of the estimate provided for in subdivision (c) of Section 10204. If the cost and expenses do exceed the amount of the bid, or of the estimate in case no bids are received or the work is ordered without asking for bids, the excess shall be paid from the general fund in the treasury.