About five times as many no-helmet biker deaths occur in states with less restrictive laws, the Centers for Disease Control and Prevention study found.
"These laws save lives," said Rebecca Naumann, an epidemiologist and the study's lead author.
CDC researchers looked at a government tally of fatal traffic crashes. They focused on 2008 through 2010 and counted 14,283 deaths of motorcyclists.
That included 6,057 bikers with no helmet. Only about 12 percent of those deaths occurred in the 20 states that required everyone on motorbikes to wear helmets.
The researchers also made 2010 cost calculations based on medical expenses and lost work productivity from motorcycle deaths and injuries.
"In 2010, more than $3 billion in economic costs were saved due to helmet use in the United States," CDC Director Dr. Thomas Frieden said in a statement. "Another $1.4 billion could have been saved if all motorcyclists had worn helmets."
In states that mandate helmets, more is saved per registered bike than in states with fewer or no restrictions, $725 versus $200, researchers estimated. When the study was done, three states Illinois, Iowa and New Hampshire had no helmet law and another 27 only required helmets for teenagers or certain other riders.
Twenty states had universal motorcycle helmet laws, but Michigan changed its law this year. Now riders older than 21 can ride without a helmet if they meet certain requirements, including carrying an additional $20,000 in medical insurance.
Motorcycle enthusiasts have argued that they should have the freedom to wear a helmet or not. They also say crashes involving motorcycles are just a small percentage of motor vehicle accidents.
According to the CDC, motorcycles account for about 3 percent of the registered vehicles on the road. But about 14 percent of the people who die in traffic accidents are motorcyclists.
Also Thursday, the National Highway Traffic Safety Administration urged motorcyclists not to wear the 5X5 brand, SA-08 model motorcycle helmet. Under federal testing, the helmets failed to meet penetration protection requirements.