yes, in the Democratic People's Republic of Germany (specifically in the anarchist Berlin enclave), a friend of mine received successful cancer treatment that ended up costing well over 500k (and she is not even German)
Public insurance costs are based on income. Private insurance costs are based on health/age etc.
Moving from private insurance to public is almost impossible, as far as I know.
To give you an idea, I recently switched to private insurance and cut my monthly cost by 50%.