Toshiba Corp. reported Wednesday that U.S. sanctions over the company's sale of sophisticated submarine-building equipment to the Soviet Union cost the Japanese electronics firm an estimated $240 million in exports to the United States in the fiscal year ended March 31. The Tokyo-based company said, however, that overall sales and net profits increased over the previous year due mainly to brisk sales at home. With the sophisticated milling machines, the Soviets were able to make propellers for submarines that make the warships much more difficult for U.S. vessels to detect. Some intelligence estimates say it could cost the United States $20 billion to counter the improved Soviet sub propellers.