By KEVIN FREKINGWASHINGTON (AP) â¿¿ American consumers have shown about as much appetite for the $1 coin as kids do their spinach. They may not know what's best for them either. Congressional auditors say doing away with dollar bills entirely and replacing them with dollar coins could save taxpayers some $4.4 billion over the next 30 years. Vending machine operators have long championed the use of $1 coins because they don't jam the machines, cutting down on repair costs and lost sales. But most people don't seem to like carrying them. In the past five years, the U.S. Mint has produced 2.4 billion Presidential $1 coins. Most are stored by the Federal Reserve, and production was suspended about a year ago. The latest projection from the Government Accountability Office on the potential savings from switching to dollar coins entirely comes as lawmakers begin exploring new ways for the government to save money by changing the money itself. The Mint is preparing a report for Congress showing how changes in the metal content of coins could save money. The last time the government made major metallurgical changes in U.S. coins was nearly 50 years ago when Congress directed the Mint to remove silver from dimes and quarters and to reduce its content in half dollar coins. Now, Congress is looking at new changes in response to rising prices for copper and nickel. At a House subcommittee hearing Thursday, the focus was on two approaches: â¿¿Moving to less expensive combinations of metals like steel, aluminum and zinc. â¿¿Gradually taking dollar bills out the economy and replacing them with coins. The GAO's Lorelei St. James told the House Financial Services panel it would take several years for the benefits of switching from paper bills to dollar coins to catch up with the cost of making the change. Equipment would have to be bought or overhauled and more coins would have to be produced upfront to replace bills as they are taken out of circulation.