MIAMI ( TheStreet) -- Hundreds of feet of decking, swimming pools and helipads may hide it well, but even luxury yacht owners are struggling.The superyacht or megayacht segment of the industry -- ships commonly defined as 80 feet or longer -- has boomed worldwide despite a slump in purchasing price. According to the 2009 Luxury Yachting Index, compiled by yachting firm Camper & Nicholsons and the Luxury Institute, there were 3,800 such yachts in existence worldwide at the end of 2008, the last year for which statistics were available. Camper & Nicholsons estimates that number is now around 4,200. In 2008, 330 superyachts were sold, 15 more than in 2007, but the total dollar value plummeted 20% from the year before, with Camper & Nicholson saying sellers were letting superyachts go for up to 25% less than their asking price. At the end of 2008, just as the global recession hit its stride, the number of superyacht listings doubled to 1,000 from 500 -- though some of those listings resulted from yacht owners trading in old product for new. However, the number of superyachts available for charter jumped to 1,000 from 830 in a year, a trend that continues today as Johnny Depp, U2's The Edge and the owner of the world's largest sail-driven superyacht, The Maltese Falcon, are letting the paying public borrow their big boats for the summer. The completion of the world's biggest and most expensive yacht -- the 557-foot, $1 billion Eclipse, owned by Russian billionaire Roman Abramovich -- earlier this year may signal a global revival of these superships' fortunes. However, the $36.5 million annual cost of maintaining the Eclipse, which is roughly the size of a Ticonderoga-class guided missile cruiser and has three helicopter pads, two swimming pools (including the world's largest, which converts into a dance floor) and a crew of 80, are reminders of how these multimillion-dollar tub toys can drown their owners in associated costs. Here are just four of the ancillary expenditures that help anchor megayacht pricing and purchasing: Berthing or mooring: According to yachting site Floating Life's technical manager Andrea Pezzini and his counterparts at Superyachts.com, there is only one yacht club in the U.S. that ranks among the best in the world: Miami's Sunset Harbour Yacht Club, with its Olympic-size swimming pool, Wi-Fi and satellite television hookups and personal concierge service. However, sliding into one of its 45 superyacht slips before browsing the Art Basel show in December or attending the boat show in February can be costly. An average mooring fee of $1,150 per day isn't great, but it costs a lot less than buying a 109-foot slip for $785,000 plus a $1,200 monthly maintenance fee. Only compared with the world's most expensive marina in Capri, Italy, where slips cost an average of $3,800 a day, is Miami somewhat of a steal.