I own a helicopter and 2 yachts, all of which are pretty underused, after all 100 hours flying is 0.01% of the year!
As to costs, insurance is 5K, Fuel £100/Hr, Depreciation, loss of interest on the capital ?, landing fees, hangarage, etc etc.
Basicaly if we all had to think too hard about the costs it would be depressing and as long as the wife dosn't find out how much it really costs, I will just keep on doing it.
Untill there is the equivalent of alcoholics annonimous for pilots, we won't stop!