I agree that this is a question which should never be asked, particularly if married to a non-flying spouse.
However, once, while confined to bed for a few weeks, I went through my cancelled checks and worked out that owning a Cessna 150 was costing me about $5,000 US per year for about 300 hours per year of flying.
Cost of 100 low lead av gas at my home field now is $3 per gallon USD. As any plane owner knows, however, this is the least of your expenses. AD on propeller anyone? The new one was $3,000 US, but it's pretty.