It may be better than the private US healthcare system, but that's not saying much.
Even leaving aside government provisioned care, there are several simple ways Medicare could use its massive purchasing power to control costs. Part A could take into account alternate available treatments and their effectiveness-adjusted-cost when determining what procedures to cover. Part B could coordinate care through a single gatekeeper physician. Part C could be eliminated, as it was a cost saving experiment that failed. Finally, Part D could negotiate with drug providers on behalf of the entire pool instead of delegating negotiation to dozens of insurance companies, each with smaller pools.
This isn't to say that the system isn't massively inefficient, just that it's maybe not quite as bad as that stat suggests :-)
That is, lots of European countries cover their entire populations with a budget of around $2000 per citizen per year. Medicare/Medicaid have a budget over $2000 for every citizen per year -- 300 million people * $2000 = $600 Billion.
(In 2010, Medicare had a budget of $453 Billion, and Medicaid has $290 Billion.)
When people call Medicare efficient, it may mean "they spend little money on overhead," but that's very different than spending it well.
What I mean is, when people say "Medicare costs the US more per member of the population (covered or not) than the UK, even though it only covers 1/6th of the population" the stat is unfairly biased - because the segment of the population that medicare covers is the segment that requires by far the most healthcare.
The stat would be dramatically improved if we accounted not by percentage of the population covered, but instead by percentage of healthcare resources used.
Why else did you think there were so many daytime TV ads for "free" scooters before Medicare cracked down? And that's just one example.
If you ask some people they would say "everything is screwed up because govt is regulating it" others say "everything is screwed up because they are not involved enough with it". I lean towards the latter, but I can buy the argument from the other side as well perhaps.