I didn't go to the dentist for a year and a half. And I got 5 cavities.

Surely, the preventative care I avoided was at least a partial cause of this. And by avoiding 2 check-ups that would have cost me $0 (outside my deductible), I had to pay over $300 out-of-pocket for the 5 cavities, with my insurer covering the other $700.

Because of my laziness/fear of dentists, we both lost.

The $0 check-up was not an effective motivator for me. But what if they fined me? What if I agreed to an insurance plan that would fine me $30 if I didn't go to my twice-a-year preventative check-ups?

I would have gone. I would have $300 extra in my pocket right now. And my insurance provider would have an extra $700.

Are we on to something here?

(Yes, I considered the idea of the provider giving me a $30 bonus for going to the appointment, rather than the punishment for not. But, A) that's a worse deal for the insurance provider, so it would be harder to get their buy-in on. B) psychologically, humans have a greater aversion to loss than a motivation for gain, so it would probably be more effective this way as well.)