Not a lot of people understand that the premiums involved in many types of insurance are mind-boggling. Many large companies self-insure where they calculate the premium is out of proportion to the risk involved.
As an example (but not specifically aviation-related), a friend owned a large hardware/clothing/mixed goods store in the country. Every once in a while, a gang would come through the small town, and indulge in break-in and theft.
After one such event, when he was cleaning up, I was talking to him and said... "Well, I guess your insurance will cover this, but it will put your premiums up?"
His answer? "I don't carry insurance on the stock. It's not worth it. The insurance company want too much, in relation to the value of the stock, for an annual premium.
I have $200,000 worth of stock here. I get broken into once every 2 or 3 years, and lose maybe $2000-3000 worth of goods. That amount is vastly less than the total of the premiums for the same period. It's a no-brainer".