Before the City Council makes any non-budgeted purchase or contract for supplies, materials, equipment or contractual services (but not including professional services), opportunity shall be given for competition. The City Manager shall have authority to make expenditures without the approval of the City Council for all budget items not exceeding twenty-five thousand dollars ($25,000.00). Any expenditure involving more than twenty-five thousand dollars ($25,000.00) must be expressly approved by the City Council. All contracts or purchases involving more than twenty-five thousand dollars ($25,000.00) shall be let to the lowest and best bid by a responsible bidder after there has been an opportunity for competitive bidding. Where an expenditure of more than twenty-five thousand dollars ($25,000.00) is involved, notice of the time and place when and where such contract shall be let shall be published in the official newspaper of the City of Pleasanton once a week for two (2) consecutive weeks prior to the time for making such purchase or letting such contract, provided, however that the City Council shall have the right to reject any and all bids; and provided further that nothing herein shall apply to contracts for professional services nor to work done by the City and paid for by the day as such work progresses.