CBO noted that even if the estimate proves correct, it will be the least expensive surface combatant in 50 year-history.
"CBO estimates the cost of the 10 FFG(X) ships would be $12.3 billion in 2020 (inflation-adjusted) dollars, about $1.2 billion per ship, on the basis of its own weight-based cost model", the report said on Wednesday. "That amount is 40 percent more than the Navy's estimate".
The US Navy had estimated that the first ten new frigate ships cost $8.7 billion, which is an average of $870 million for each ship, the report said.
Several months ago, the Navy awarded a $795-million contract to Fincantieri Marinette Marine to build the first ship.
According to the contract, Fincantieri will build the first ship designed for a class and then provide the US Navy with options to build nine additional warships.