If that really is the problem then you, as a freelancer, can hire a company to navigate and negotiate the health care plans for you and other freelancers as a pool and get the same quality and discounts as you would in a large corporation.
But even so, they'll be a middle-man and they'll try to take as much profit from the group discounts they get instead of passing those savings on. An employer doesn't have an incentive to make profit there.
I don't know, do they? If they do, then your premise is correct and there's enough benefit in negotiating in groups that it's worthwhile. If there aren't, then it's either a) the "economist sees a 20 on the ground and immediately assumes it's fake because someone else would have picked it up otherwise" or b) your premise is wrong and having a large HR department doesn't make a difference in your plan costs and pricing.
The real answer is that they do exist. I used Oscar for a year and their plans were actually by either United Healthcare or Aetna (I don't remember anymore) and the premiums were less and the quality was identical to what I had through a company provided insurance later. There's also Justworks that does something similar, though they're more of a full HR service provider.
