Simply put. Cash is king. If you have cash, any bill arising out of a ER stay can be negotiated.
Years ago, after an auto accident, I helped a woman with a staggering problems. Seriously injured, her hospital bill (not counting doctors charges) was a over $120,000. Because she only had $30,000 in insurance proceeds available, we were able to settle the entire amount for that amount. No collection agencies, no bad marks on her credit. Why? The collections people at the hospital want to collect as much money as possible, as quickly as possible, and for the least cost/effort. They understand money in hand is in their best interest.
Last year, I had an unexpected trip to the hospital. Despite having medical insurance, my plan was a high deductible plan and I ended up with a significant amount of uninsured loss to deal with. Since that time, I have been paying off the charges systematically with monthly payments. As of today, all that remained was $650. Instead of continuing to pay $50 per month, I called up the provider. Claiming that I had just received my tax refund, I offered $500 to make the debt go away. They took about 30 seconds to accept my offer.