The $7.3 billion Fairfield Sentry Fund invested solely with Madoff, taking a cut of 1 percent of assets and 20 percent of gains, which averaged about 11 percent annually in the past 15 years, according to data compiled by Bloomberg. Fairfield Greenwich is one of at least 15 hedge-fund firms and private banks, including Tremont Holdings Group Inc. and Banco Santander SA, that earned similar fees for sending customers’ cash to the 70-year-old money manager. “It’s mind-boggling that people like Tremont and Fairfield Greenwich had been doing this for...