Here's my short story from the horrors of the US health care "system."
(and yes, I know it's nothing like the travesty that other folks go through)
I needed a CAT scan- no biggie. Drink this goop, show up at this time, needle in the arm, etc etc etc. The office for this is across the hall of the building that my doctor is based in, and is run by the same group. Convenient, like that. BIll comes some time later.
Now, let me stop here to inject this: I have, by most in the US's standards, very good health care. Lots of things covered, relatively small co-pays, etc etc etc. But it's a Tiered plan.
What's that? Oh, it means that some providers are Tier 1, and are pretty inexpensive to use. Some are Tier 2, which are more expensive. I guess there's a Tier 3, but I'd rather not know about it.
Anyway, back to the story.
Bill comes, and what do you know, the place that did the CAT scan is a Tier 2 facility. Or a Tier 2 provider did the scan in the facility. Or something. So instead of a Tier 1 (with, in this case, a $50 co-pay), I get a Tier 2 (with a $1000 co-pay). And there's nothing to be done about it. Pay up, sucker.
That's what happens on a "good" health plan in the US.