Since Simon Kuznets developed the useful concept of Gross National Product in the 1930s, many critics have pointed out one of this major flaws: by aggregating the dollar value of all goods and services exchanged in an economy, it can "reward" some horribly inefficient behaviors in the form of higher GNP. With the assumption that a higher GNP/GDP is a sign of a stronger and better economy, the most valuable citizen is not an entrepreneur, a laborer, or an inventor. It's a terminal cancer patient who just wrecked his Lamborghini and is going through an expensive divorce. Think of the billable hours he generates for the legal profession. Think of what his hospital bill will be when all is said and done. Look at all the Economy he's generating.
The point of the morbid example is simply that not every form of economic activity is inherently "good." The American economy could hugely benefit, for example, from bombing several major cities (what a boon for the building trades!) or infecting half the population with some long-lasting and expensively treated disease. Most of us would prefer that economic growth result from something less dismal.
Similarly, single-payer is beginning to attract support from more than just the far left lately. Don't misunderstand – I don't believe SP is coming soon or that huge majorities of Americans suddenly support it. But it is transitioning into the mainstream of the health care debate, which eventually will have a positive effect on policy. You can tell it's being taken more seriously because the campaign of concern trolling against it has intensified noticeably during this session of Congress.
The LA Times has a decent piece on three prominent types of SP concern trolls – "We need more details," "It's too expensive," and "It'll never happen" – but I believe another important kind is absent: the "Think of all the middlemen of the health care industry who will lose their jobs!" troll. The Chamber of Commerce, reliable organ of Business writ large, is most aggressively pushing this narrative. You know they must be worried if they're willing to pretend they care about The Working Man's job.
Conceptually, it isn't difficult to imagine a switch to single payer eliminating some jobs. The administrative bloat in our healthcare system is beyond most people's comprehension – I've had the misfortune of seeing it from the inside earlier in my career. People whose days consist of filing and refiling and appealing and refiling various insurance claim forms and managing the labyrinthine network of medical records are two tasks that involve more person-hours than you can imagine. A single payer system would de-complicate those issues at least somewhat if not entirely, and the paper pushing jobs our current system creates so readily would decline.
Other generally pro-SP estimates argue that a changeover would create jobs in the long run. It's a very difficult thing to forecast and there's no way to resolve the different predictions at this point. What is undeniable, though, is that "It employs a lot of people" is a very bad reason to keep a healthcare system as it is. The ability to access basic medical care without risking long term financial ruin should be a fundamental compoonent of any society that considers itself civilized. And for an issue on which costs and inefficiencies are brought up constantly, sticking with the current system because it creates a ton of jobs for middlemen, rentiers, and layers of superfluous bureaucracy is a very bad argument. The system's inefficiencies bloat costs and need to be eliminated, but they also create jobs so should be kept? C'mon guys. Pick one.