Earlier quoted context omitted.
Most medical procedures are not emergent. It's hard to shop around for emergency care, but shopping around for everything else is pretty straightforward. We have strong experimental evidence that when people are not insulated from price, they shop around and consume less medicine with no measurable effect on their health. http://www.rand.org/health/projects/hie.html
This article suggests that shopping around for, say, knee replacement surgery, is not so simple: http://www.washingtonpost.com/blogs/ezra-klein/post/how-much...
She tends to get accurate estimates, probably because hospitals don't like to hear "I thought it only cost $X, I don't have $X + $Y, so, umm..."
Granted, what she gets isn't likely to be a "a complete cost estimate [...], [...] reflective of any negotiated discounts, [...] inclusive of all associated costs, and did not identify consumers’ out-of-pocket costs", which is what the GAO wanted. But it's certainly good enough for shopping around.