Lets see, in my accident last year I wasn't wearing a helmet but, very luckily had no head injuries. Just mangled ankles. This cost my auto insurance max limits on my uninsured motorist policy and collision. Cost my health insurance God knows how much cumulatively to fix my legs and get me walking again. (They're still paying for physical therapy over a year later.)

Now if my brain would have got splattered right there on the road, I imagine my health insurance would have got off a lot cheaper.

Point being: I don't think a helmet-less biker is necessarily more expensive than a helmet wearing one in an accident.