It's irrelevant how much they spend on premiums, because they are the ones who set prices of procedures and drugs. There is no one to step in and introduce hard price controls, because it doesn't benefit anyone on the gravy train, just the consumer.

Imagine if there existed a company whose only job was to buy oil from OPEC and deliver it somewhere else. They could say "we spend 99% of our revenue on oil! look at how efficient we are!", ignoring the fact that OPEC is a cartel that sets prices, so not only can they be vastly overpaying, but the amount of oil purchased can be wildly inadequate to cover the needs.