You know it is springtime in London not by the arrival of swallows or the sprouting of blossoms, but by the printing of the annual Sunday Times Rich List. This is a sort of league table for the superrich, a survey of the British wealthscape that decrees who comes out on top—usually steel baron Lakshmi Mittal. In publishing this list, The Sunday Times has made the acquisition of extreme wealth into a spectator sport. But being rich has always been a competitive business.

We live in strange times. On one side the wheels are falling off the world economy; food and oil prices are shooting up while property values head in the opposite direction. Yet at the other end of the socioeconomic seesaw, the big issue occupying some intelligent minds this summer is whether their superyacht is big enough.

According to Philippe Lamblin, the silver-tongued CEO of Privatsea, which sources large boats for people with large bank balances, the threshold for superyacht status used to be 30 meters. Today that is not nearly enough to keep status-obsessed plutocrats from feeling inadequate. Lamblin recalls joining the cruise of one of his clients and putting in at a harbor in the Mediterranean next to someone he knew; the problem was that the boat they were berthed beside was 55 meters—some 20 meters longer than the one they had been enjoying for a week. As he recalls, "We went aboard for a drink, and after we left, the guy I was with said, 'You know what? Next year we go bigger'."

Once upon a time, Aristotle Onassis dazzled the world with the Christina O, which at just under 100 meters was considered a floating palace. But today, no self-respecting aspirationally minded, competitive billionaire would be so easily satisfied. Roman Abramovich is said to have commissioned the world's largest yacht. Called Eclipse, it has been reported to be almost 170 meters long, comfortably overshadowing Rising Sun and Octopus, the yachts of Larry Ellison and Paul Allen, respectively.

The thing about luxury goods is that while they may look like boats, cars, wristwatches or works of art, they are, as often as not, scorecards. Up to a certain level of luxury, there is comfort in showing each other that you can keep up, using well-known signifiers (a certain brand of watch, holiday destination, motorcar, etc.). But as merely rich escalates into unspeakably wealthy, people use possessions to set themselves apart from those who wish to be their peers.

And it is for such people that the luxury world has created limited editions. The Aquariva, for instance, is an elegant powerboat that at 10 meters and €450,000 makes for a lovely bauble. However, for those seeking a bit more who were prepared to pay an extra €50,000, a few years ago Riva decided to make 10 specially trimmed Aquarivas, with a plinth-mounted champagne cooler and a leather picnic box. According to Riva, all 10 were sold on the first day of the 2006 Genoa Boat Show. Riva has learned from this lesson; it is linking up with the classic Mille Miglia car race to make a series of limited-edition Riva boats, the first of which will be auctioned at the rally.