I think this is pretty common. If you get a hospital bill and the insurance already paid a lot, call up the hospital and complain, and it will often be lowered. This happened to me once, a $15k bill was reduced to $3k. The insurance had already paid $50k or so. Hospitals don't really seem to care about the extra portion the patient is supposed to pay. The try to get it, but don't make much fuss when you challenge it, since they already got what they really wanted, the insurance company's money.