WASHINGTON (MarketWatch) -- The price of retail gasoline would fall by half, to around $2 a gallon, within 30 days of passage of a law to limit speculation in energy markets, four energy analysts told Congress on Monday. Testifying to a House Energy and Commerce Committee subcommittee, Michael Masters of Masters Capital Management said the price of crude oil would drop closer to its marginal cost of around $65 to $75 a barrel, about half the current $135. Fadel Gheit of Oppenheimer & Co., Edward Krapels of Energy Security Analysis and Roger Diwan of PFC Energy agreed with Masters' assessment at the hearing. Other witnesses say speculators aren't a major factor in oil prices, however.