[ithkuil]

This can be solved easily: let the insurance company pay the ransom, and factor in the full cost (since it wouldn't be tax-deductable) when computing the premium.

EDIT: otherwise, the collectivity effectively pays for what you deducted from your taxes. The missing money on the overall country balance has to come from somewhere.

EDIT2: If you're talking about private insurances covering your risk of ransoms, this means you assume it's your responsibility to pay for your losses (insurances just allow you to pay proportionally to the risk), and not e.g. have the government, say, paying it for you (through public funds, which can and IIRC has happened for kidnapping cases here some countries pay the cost of rescue). All I'm saying is that if it's private insurance, it should be private 100%