Hospital consolidation allowing hospitals to charge monopoly rents can be solved with single-payer, antitrust enforcement, or ideally, both. In rural areas, however, there may not be enough demand to support multiple hospitals.
The inefficiencies created by numerous intermediaries can be solved with single-payer. Administrative expenses in the US are far higher than anywhere else.
Drug prices would be reduced under single-payer, provided Medicare was actually allowed to negotiate prices and establish a formulary. The WSJ article talks about Humira in particular. An NYT article about Humira from January, citing a 2015 source, says:
Similarly, the $600 EpiPens (which IIRC actually cost closer to $300 after average PBM rebates were applied, but that is still excessive) are cheaper elsewhere: about $68 at current exchange rates in the UK under the NHS.
These are only a few high-profile overpriced drugs. There are many more.
There is also the advantage that doctors can easily familiarize themselves with a single Medicare formulary and consider cost in their prescribing decisions. In many cases, there are multiple drugs that could be used to treat a condition, with similar side effect and safety profiles. PBMs currently establish formularies, guidelines, and may require step therapy for some drugs (which requires the patient to try lower-cost drugs first, unless there is some reason not to, and step up from there if they don’t work). This is a pain for doctors to deal with because there are numerous PBM formularies out there (even from the same PBM), and different PBMs have different negotiated deals, so the lowest-cost drug to one PBM may be the highest-cost drug to another. One formulary for everyone would be easily manageable; dozens of them depending on the patient’s insurer, plan, and PBM formulary is not. Not to mention that if/when the patient switches insurers, it may be necessary to go through the entire authorization process again and potentially try different drugs if the new PBM’s requirements are different.
Suggesting that doctors could simply go cash-only to solve this problem is naive. For one, cost-sharing discourages use even when the use is medically advisable, and we shouldn’t discourage the use of primary care – it’s way cheaper to resolve something via primary care than to risk it turning into a hospital situation later. Second, it’s not a solution for catastrophic risks – e.g. a cancer diagnosis, a major accident, or any other serious condition – as most people do not have the means to self-insure for such risks. (It’s also inefficient to do so.) You could then suggest a combination system of cash-only for cheap services like PCP visits and private insurance for higher-cost services like hospitals, but then you have the same administrative bloat on the hospital side while discouraging cheap primary care use. It’s the worst of both worlds.
In general, cost-sharing works when the insured has some ability to eliminate or mitigate damages. For example, your auto deductible encourages you not to leave your car somewhere unlocked with the keys in it. Healthcare is different – things are often just random (or we later find out that something thought to be safe actually wasn’t), and the patient already has “skin in the game” by virtue of, well, their health being involved.