In order to make the calculation 'correctly', don't forget to price in the correct amount of risk. As an example, say there is a 0.2% chance in any given year of your house catching fire, either through your own fault or from a neighboring property on fire. If there is a 50% chance of you being able to rescue the money in such a situation, then that is an estimated 0.1% loss in any given year. There is also a similarly priceable risk for theft etc, which would probably increase with the amount stored. If it becomes known that there is 500k in cash stored in your house, there are probably plenty of people greedy or desperate enough to break in with heavy tooling when you're out and steal the whole safe.