The Italian firm of Breda Costruzioni was the apparent low bidder yesterday with a $76.4 million offer to build 94 new subway cars for the Washington Metro.

Breda's bid was $16 million lower than that of the apparent second low bidder, the Canadian Car Division of Hawker Siddeley Canada Ltd. The Budd Company of Philadelphia, which is now German owned but is technically the only American firm still building transit cars, had the highest bid, of $103.3 million. Metro's estmate for the work was $77.6 million.

Officials for Breda said that they would meet the Buy America requirements of federal law by assuring that a least 51 percent of the new cars American origin. Many subsystems will come from American firms and, Breda said, the cars will be assembled in the United States as close to Washington as possible. Eighty percent of the cost comes from federal aid.

Metro plans to formally award the contract by July 1. The schedule calls for the first car to be delivered in June of 1981. By that time, Metro will have opened three more extensions to its present 31-mile system and the original car purchase of 300 units will no longer be adequate.

The price of subway cars has risen dramatically since the Metro program began. Metro bought its first 300 cars from Rohr Industries in 1972 for a fixed price bid of just under $300,000 per car. It was Rohr's last contract in the transit car business and Rohr claims that it lost $45.8 million and field a $48 million claim against Metro that is still pending.

The Breda cars will cost either $740,000 or $791,920 each, depending on the type of power controller used. CAPTION: Illustration, Metro: The Latest Racy Italian Car