I had a problem similar to this about two years ago. 9 hours in the ER on a Friday night to get checked out for a pain cost $13,000. I had to pay around $100 upfront, and then insurance kicked in and took care of the rest.
The way hospital balance sheets work these days, they charge you that much to subsidize the many patients who (a) could not afford health insurance, (b) are unemployed, underemployed, or employed without health insurance benefits, (c) avoided preventative health care and healthy lifestyle choices like most Americans, (d) went to the ER as their primary care provider, long after they should have first visited a doctor about preliminary symptoms but could not afford to go, (e) could not legally be turned away by the ER, and (f) had absolutely no way to pay for their care even if they wanted to. The fact that your insurer had to pay almost $13,000 is the point of the individual mandate in health care reform. Otherwise, the only way to keep ERs from closing (and many ARE closing) is getting people like you and your insurer to subsidize the people that use no insurance, get no preventative care, do not manage symptoms and walk into the ER as disasters.
That is crazy. A couple of months ago I had to go to ER, was there for 2 hours or so, and went home. A week ago I got a bill of £12 for the penicillin they gave me for a week, as that wasn't for inside hospital. I'm not insured (in the UK), and I don't pay taxes (anywhere).