Turn the key of a 71-meter-plus yacht and 10 minutes later you will have spent €400 ($540) on fuel, according to research by yachting Web site Superyachts.com . Cruise to Porto Cervo in Sardinia in your 50-meter boat, and a berth in the marina will cost you over €2,500 a day, according to Swiss yacht management company Floating Life.

Owning a super yacht is obviously an expensive hobby. Super-yacht prices range from around €3.5 million for a 30-meter boat to more than €135 million for a 71-meter-plus mega yacht. But few people realize how the running costs can mount up.