I don't see what this has to do with whether or not people can make rational cost-benefit decisions with regard to healthcare. Where is the market failure? Are you implying that doctors will try to up-sell you on various treatments, and there's no way you can find out if they're cheating you? My vision of the future is that you go to the doctor, and he presents you with a range of options, including the prices for each. If, for some reason, you think he's dishonest (and perhaps a quick perusal of Consumer Reports or Angie's List or WhatsUpDoc.com

or DoctorWhat.com

will confirm this), then you can get a second opinion.
It's not a matter of mere pricing consideration, nor is it a matter of cheating. It's a matter of having the knowledge required to make a good informed decision as a consumer.
As a consumer, the choice to buy something isn't based solely on the cost of the product. It's also based on it's utility to you and it's perceived value to you. Then you weigh those elements against budget and price. This is of course severely simplified, but the concept should hold for our purposes.
I'll use my own experience as a platform for this, because I think it will be easier to follow with some specifics. Several years ago, I had a uterine fibroid that was undiagnosed. It was interior, so it wasn't palpable during my regular pelvic exams. I had some symptoms that would have suggested a fibroid, but the symptoms manifested over the course of several years, to several different doctors - I had idiopathic hematuria, I was osteopoenic, and anemic. The hematuria manifested to my PCP in 2007, the oseopoenia was identified by an orthopedist when I had a stress fracture of my tibia in early 2010, and the anemia was diagnosed by my gynecologist in late 2010. Just a month after the anemia was diagnosed, the fibroid hemorrhaged, and I nearly died.
The emergency room doctors stabilized my blood loss, and identified the problem. At that point, it was up to me to go back to my gynecologist and figure out what to do about it. My gynecologist listed three options: hysterectomy, myomectomy, and arertial embolization. She was qualified to do the hysterectomy, and gave me information about that procedure... but the other two procedures were performed by two completely different types of doctors, and she knew little about them other than the very basics.
So I attempted to do research on my own. Of the three, only one (myomectomy) preserved my fertility, but since I didn't plan on having children, that wasn't a large concern for me. Both the myomectomy and the arerial embolization left me open to the possibility that the fibroid could grow back in the future. All three had different rates of complication, different recovery times, and different impacts on my life. Unlike cancer, which has pretty well documented probabilities of survival and recurrence, those stats aren't as easily available for other conditions. Trying to find actual statistics and details for the rates and types of complications for each option was incredibly difficult.
And all of this is before I even begin to consider the difference in cost.
And to add some fun to the mix, I needed to make a decision within about two weeks - well before my next menstrual cycle began, where I would likely hemorrhage again and run the risk of bleeding to death - again.
I managed in part because I did NOT try to do all the research, and because I decided I didn't give a @#$@$ about the cost. I didn't have time to find out all the things I actually wanted to know, and I went into it feeling rushed and uncertain, and not at all informed.
I settled on a myomectomy, mostly because it left me the option of having kids if I changed my mind, and also because the doctor who would perform the surgery was highly recommended - NOT because I was well informed about the choice I was making.
Even once that choice (of sorts) was made, it didn't end there. There were still questions about drugs to take prior to surgery in order to halt my menstrual cycle so I didn't bleed to death, and to try to build up my red blood count so I'd survive surgery. And when that didn't work, there were decisions about blood transfusions. I was no qualified to decide whether or not the drug recommended to me was the right drug to take, or whether it was too expensive. I just took it so I didn't bleed to death. I wasn't in a position to make an informed decision about whether or not I wanted a blood transfusion, or even to consider the risks of a transfusion... because without it I would not survive surgery.
So tell me... how exactly do you believe a "good consumer" should behave in a situation like mine, and what exactly do you think constitutes "well informed" decision? Do you think that "a little research on the internet" is sufficient for me to actually know anything at all about what the right treatment approach is?
Bear in mind that I probably have more knowledge and more resources at my disposal than most average consumers. I at least know how insurance works, and I have several very knowledgeable case managers, nurses, and doctors at my disposal. Most people don't have that luxury, and can't just holler at a trusted coworker for advice.