This is where a quasi-union situation "helps" the employees. See insurance companies would be happy to offer plans to everyone individually, at 10x the cost, since they have everyone in a ringer (near-monopoly) everyone has to pay whatever price they set, same problem with medical care itself, by the way, not much competition when you are looking for a surgeon skilled in neurosurgery or whatever. But with corporations, they swing a big stick and can force the few insurance groups out there to compete with each other since the company represents such a large block of individuals. They can force the insurance companies to put together group plans that cost less for the individual at least at the outset. See here is where it gets seriously complicated. How does the insurance company offer a lower price to compete for the corporate dollar? They try to contract with certain doctors who are willing to accept set rates for certain procedures, or types of procedures, so the insurance company pays them less when there is a claim. But doctors can only cut so low before they can't cover overhead and a staff and insurance of their own (malpractice is a huge cost).
I have a friend in Phx who is an independent family practitioner, and he has told me he is trying to restructure. See it is very uncommon to be independent anymore. Nowadays the "family doctor" is more often than not on the payroll of, you guessed it, an insurance company. So my friend is seriously feeling the pinch. He doesn't want to be constrained by what the insurance companies would tell him do if he were working for them directly, but they force him to take much lower payments than if he were simply salaried to them, if he wants to accept their insurance. So now he is trying to figure out a way to stay independent, but it is a losing battle. He told me his true income has dropped by almost 40% over the past decade, after paying all costs of his own, while his office is taking in more money than ever. And the care he can give is worse, as it is tainted by what the insurance companies are willing to pay for.
It is as broken a system as there ever was really. We have the very best medical care in the world, but accessibility is terrible and the care could be even better than it already is if we could find a way to balance out the money side of the equation.