Original poster: persevero
Medical bills. This came up in a recent (really excellent) SS/HG, and I've encountered it before. In Britain, Muggle medical care is free at the point of use. Not just for poorer families, but all of us. Of course long-term illnesses cause financial hardship, especially if a breadwinner is unable to work, but we don't usually pay medical bills as such.
I'm sure someone will get back to me on the details here - I acknowledge that the system is far from satisfactory and that queues for, say, hip replacements, may mean that people struggle to find the money to go private, but certainly a person with leukaemia should have no medical bills at all.