A new birth control method for men has the potential to win as much as half the $10 billion market for female contraceptives worldwide and cut into the $3.2 billion of annual condom sales, businesses dominated by pharmaceutical giants Bayer AG, Pfizer Inc. and Merck & Co., according to estimates from the last major drug company to explore the area. India's reversible procedure could cost as little as $10 in poor countries, and may provide males with years-long fertility control, overcoming compliance problems and avoiding ongoing costs associated with condoms and the female birth-control pill, which is usually taken daily.