What are some typical costs associated with major unexpected health issues a young adult might have?

I’m a healthy, normal-weight, non-smoking 30-year-old male. I’m shopping for health insurance just to cover any unforeseen major illnesses or injuries that might come up. I’d like to get a ballpark estimate for how much these things cost, so I can better judge the level of insurance to buy.

So, what are the most common health problems that a relatively young and healthy person might have, and approximately how much do they cost to treat?

Thanks!