Will this Insurance cost a lot?
Like in real-life insurance should be a relatively small part of your regular in game expenses which will also include paying landing fees, trade tariffs (if in a system with lots of infrastructure and law and order), fuel (if you dont collect it yourself from a gas giant), buying cargo to trade, hiring help, making upgrades to your ship or even buying a whole new ship.
Some of the additional policies like upgrade or cargo insurance will be rated based on risk levels. Risk level 1 being the safest systems and risk level 5 being the most dangerous system that is insurable for cargo or upgrades. Any risk level over 5 is un-insurable. A risk 3 policy for cargo will cover you for all cargo losses in a risk 3 system or below. The higher the risk level of the policy the more it will cost. As with the base insurance this will not be crippling financially but instead be a reasonable running cost that relates to the risk / reward profile of the systems flown.