To build a swimming pool in Britain is the triumph of hope over experience. To buy a yacht, wherever in the world you live, is to enter a whole other league of delusion. Ocean-going, you might say. It is to attach a hose to your bank account and leave the tap running.
This is the painful realisation JK Rowling has come to, having put her schooner up for sale for £7 million ($12 million) less than she paid for it. The loss is particularly dramatic since she only bought 155ft Amphitrite back in January (from Johnny Depp, as you do), for £22 million ($39m). Yet the classically styled yacht, with berths for 10, is already back on the market for £15 million ($27m) - a collapse in value of almost £1 million ($1.8m) per month.
Even for a billionaire author, this has been one expensive summer!
Poor JK was clearly badly advised. But she is not alone in having her fingers squished by the jib cleats of boat ownership.
In fact she joins a whole flotilla of yacht widows, women whose lives have been dashed on the rocks of the big sailing conspiracy.
It goes something like this. You go on holiday to Corsica. You have a lovely lunch in the quay, surrounded by glamorous people and their shiny clinking vessels. You think how marvellous it would be to spend a summer in the Med, bobbing freely from island to island, diving wherever you please. Just think of the hotel bills you would save.
You then Google a few boats. They're really not as expensive as you thought. Quite a good investment in fact. Look, there's an old trawler ripe for conversion for less than the price of a cottage in Cornwall. Wouldn't it be fun? And so it goes on, the fantasy of lazy late lunches and sundowner cocktails on the poop deck.
What you do not think about are the hidden costs: the mooring, the winter storage, the maintenance, the insurance, the crew, the port fees, the MOT, the replacement equipment - oh, and did anyone mention diesel? Unless you plan to do some actual sailing, these yachts are jolly thirsty.
As with horses and classic cars, the initial outlay is only the beginning. Horses in particular are deceptively reasonable. A few grand will get you a handsome bay hunter. Then you're handed the reins, and the bills start flooding in: livery, vets, antibiotics, feed - and that's before you've entered your first gymkhana.
The same applies to old cars: you fulfil your fantasy of owning an E-type for the cost of a new BMW. But then it runs a big end. Uh oh. Here comes a bill for £10,000 ($18,000).
We don't know exactly why JK is selling, but we do know why she bought. After chartering Amphitrite for a holiday, she said she was so entranced that she had to have it. And therein lay her mistake. She allowed herself to be swept away by the lie that owning is better than experiencing. It's the reason so many lottery winners end up bankrupt.
According to a study by Camelot, 44 per cent of them lose it all within five years. Nobody tells you that a new Maserati loses half its value within minutes of leaving the forecourt.
The truth is that unless you actually are a billionaire, the key to enjoying the high life is to keep your investments separate from your toys. Rent a 10-berth schooner, sure, but don't buy one. Because as they say at Cowes, the happiest moment of your life may be when you buy your first boat. But the second happiest is the day you wave it goodbye.