Should Sam's Club pay the same prices for merchandise as Mom & Dad's Local Market?
There are some legitimate reasons for price discrepancies between what insurers pay and what individuals pay, though there are many dubious ones as well. A bigger problem is that insurance is only a small part of what most 'health insurance' companies really do.
To use a rough analogy, would it be reasonable for someone to buy "oil change insurance" for an automobile? To be sure, some people do buy automotive service plans which include oil changes, but would anyone call such a plan "insurance"? Insurance is based upon the notion of protecting people from unexpected events. By contrast, many if not most of the payouts by "health insurance" companies are for things which are entirely expected.
If some employees need medicines that cost $50-$250/month, an employer that helps cover such costs may boost employee satisfaction by doing so. The notion that such a thing is "insurance", however, is ludicrous. If an HMO can act like Sam's Club and use quantity discounts to save more on medicines that it spends distributing them, that's fine. But that doesn't mean it's "insurance".
The only difference is marketing costs and collection costs. It's doubtful the insurance company saves much on marketing, since the consumer usually is picking the doctor and most insurances have a large selection of doctors. It's also doubtful that the costs of collecting from individuals is any worse than collecting from insurance companies.
Should Sam's Club pay the same prices for merchandise as Mom & Dad's Local Market?
Sam's club buys in quantity. I don't think insurance companies do. The negotiation power that insurance companies have isn't from guaranteeing a volume purchase. They negotiate the same rates whether a doctor does 1 surgery or 10,000. It's simply that the insurance company has inserted themselves between the doctor and patient. And while the insurance company doesn't promise the doctor any more volume, they can eliminate the doctor from the consumers options. Thus if a doctor wants to play at all they have to give the insurance company discounts, which means they have to mark their standard rates way up.