So St. Jude's says that you don't need to pay them back for staying at their children's hospital. Can someone help me understand how they can do this legally?

St. Jude will ask the affiliate care provider to bill your insurance. If your insurance will not pay or you do not have insurance, all treatment costs are covered. Having the costs covered by insurance and generous donors allows St. Jude researchers to make major progress in curing childhood cancers and other life-threatening diseases. This helps make sure no patient or patient family ever receives a bill from St. Jude.

-alyssa :P