Abnormally low bids can cause combined authorities (CAs) a number of problems. Most important being that if the supplier is awarded the contract, they may struggle to deliver the contract at the stated price, and may seek price rises (or may go out of business!).
Other bidders may also complain that the contract award violates the principle of equal treatment. In other cases, unless this is picked up as part of the evaluation, the bidder may have cut corners to achieve the low price, so the quality will be poor and the CA will pay the cost in both money and quality.