Personally, I think you are being far too simplistic, and erroneously equating insurance with purchasing a product.
On the simplistic side, I don't agree with your cost delta. That may very well be the printed bill delta, or the price one is asked to pay without insurance, but no insurance company is out laying $40k for an ambulance, an overnight and observation. But I do agree that there is a delta.
A middle of the road insurance plan for a family costs $24k per year (ACA sets a lower #, but that is largely to trigger Cadillac revenue). This means that an average family is using $24k less margin for insurance company per year. Most families don't use a fraction of that, but they collectively buy into a pool to cover themselves in case their own specific lifestyle choices push them over that average. Insurance is a fear buy: I don't want it, but I am afraid to pursue my life without risking my assets without it.
So to your cost question: the true cost delta is irrelevant for bicycle head injuries, just as the true cost of cancer treatment is irrelevant. By purchasing the product, you have placed your lot in the same hat as everyone else in the same boat. If you want to pay less, then throw your lot in the hat with an experience rated group that has an exclusion for bare headed cyclists. I would wager that that group may well have other exclusions that you will need to abide.
The HSA movement is about passing costs on to users, to drastically drop premiums and reduce experience rating impacts. Join a group like that if you want to reduce your out of pocket impact from others decisions.
Or carry no insurance. You can pay doctors office visits and pay for scrips, and you won't pay a fraction of $24k per year. But you also won't have other people's money bank rolling your colonoscopy.