What are the chances of you having a heart attack or cancer? There are ways to calculate your personal risk levels, refer to:
If you developed cancer and one of the drugs recommended was not Pharmac approved in New Zealand (not paid for by the Government) the cost could in the order of thousands of dollars.
Without insurance where will the money come from: friends?, family?, mortgaging your home?
Also check out the Longevity calculator, Life Expectancy calculator