The price the dealer in Treasury bill is willing to buy the bill.
T-bills is a type of money market instruments used to raise short term funds. It is sold in a secondary market; it is also a short term debt obligation backed up by the federal government.
T-bills have a maturity date of less than one year, normally three months. These transactions are done through the dealers at the bid price quoted by the financial press which is the price the dealer is willing to buy.