Medical billing systems drive up the cost of commercial health insurance. One way to ease that strain is to get more low-income people on Medicaid. Hospitals have to collect as much as it costs them to take care of their patients. That is hard for small hospitals, most of which are rural. Those costs include not just the services that individual patients realize they received, but also a share of the salary of the maintenance crew, the light bill and the cost of replacing the stained carpet.Different payers have greatly different abilities to pay, so the hospital has to charge its costs to whoever can pay them. Otherwise the hospital will go broke and close.Understanding the general pattern of hospital and medical bills can help a patient or voter understand why Medicaid expansion is important for them, why “self pay” patients are at risk of bankruptcy, and why their insurance bill is so high.