How helmets save lives?

In our case, it certainly helps and the people who claim it not are making mistakes.

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There are different unique motorcycle helmets in the market that are upgraded versions. Helmets should be the primary gear when you guys are traveling.
The life expectancy and risks of getting serious injury get reduced by 69% claimed by research. Helmets should be there with you all the time, it prevents your skull from being cracked open.
Even if you get injuries or are met with an accident with a helmet on, there will be miro injuries and are treatable. But if helmets are off the table for you, then you might even risk your life.
A tip, neither wears a helmet too tightly or too loose. According to the manufacturer’s recommendation, I should be able to put one finger in between the chin and the chin strap.

Well, how much you should spend on a helmet? The first thing you need to keep in mind is quality. Don't compromise your life for few bucks.