Has anyone w/o health ins gone to court when doc is suing for huge pymts?

My sister was inbetween health insurances in her job, and of course, needed emergency gall bladder surgery. The surgeon wanted $4000, they agreed on $2000. She had the surgery, and when she told me the cost, as a Medical Biller I advised her that ins co have fee schedules and would pay between $500 and $900 depending on the co. So now the doc is suing for the $4000. Has anyone had a court experience with a doc suing for pymt?