Snaafi Dancer Bought by Sheikh Mohammed, the crown prince of Dubai, in 1983 for a then world record of $10.2m (€7.1m at today's rates), Snaafi Dancer was sired by Northern Dancer, the most successful sire of the 20th century.
But while his father raced for two years, winning 14 of his 18 races and never finishing less than third, his expensive offspring didn't even race once.
He was deemed by his handler John Dunlop too slow to race and then, to add insult to injury, turned out to be subfertile, managing to sire a paltry four foals.
The 24-year-old horse, a legend in racing for all the wrong reasons, is retired in Florida.
In 1985, British racehorse owner and breeder Robert Sangster led a syndicate that bought Seattle Dancer for $13.1m (€9m now), still a world record.
The horse was sired by Nijinsky II, a British champion, and was half-brother to US Triple Crown winner Seattle Slew.
However Seattle Dancer, who trained in Ireland, raced just five times, recording two wins and career earnings of $150,000 (€104,000).
While his racing career was a flop, Seattle Dancer was at least more successful as a sire. He is the sire of 35 reported stakes winners and his offspring had by the beginning of this year earned a reputed $29m (€20m) in winnings.
Much feverish speculation surrounded the debut race in October last year of Jalil (left), the most expensive horse ever to race in Britain.
The colt of Storm Cat, a sire with 24-hour armed guards and whose owners charge half a million pounds for each live foal sired, cost a reported $9.7m (€6.7m).
He made his debut as a strong favourite in Newmarket, ridden by Frankie Dettori -- but was soundly beaten. The horse managed only a lowly sixth out of 13 runners.
Jalil is owned by the Godolphin stable, which is owned by Sheik Mohammed, who will hope he has not shelled out millions of dollars for another Snaafi Dancer.
Born in 1981 and sired by the successful Northern Dancer, Sadler's Wells achieved racing and later breeding fame in Europe.
As a three-year-old in 1984 he won the Derrinstown Stud Derby Trial, the Irish 2,000 Guineas, the Eclipse Stakes and the inaugural Phoenix Champion Stakes.
He also finished second in the Prix du Jockey Club and King George VI & Queen Elizabeth Stakes. His real success, however, came when he retired from racing. He has been champion sire 14 times and his offspring have included more than 200 stakes winners. The horse serves around 200 mares each season, with each mating earning up to £200,000 (€278,000).
Commander in Chief
A British thoroughbred, foaled in 1990 by Dancing Brave, who was European Horse of the Year in 1986 (above). His illustrious ancestors include the 1972 Epsom Derby winner Roberto and Lyphard, a son of Northern Dancer.
The horse won the 1993 Epsom Derby, beating the odds-on favourite Tenby even though he had not yet raced as a two-year-old.
The 'Racing Post' had not included him in its list of horses to watch in 1993.
But in the same year Commander in Chief won the Irish Derby Stakes and was named Cartier Three-Year-Old Champion Colt.
In winning the Derby he captured a title that had eluded his champion sire.
Commander in Chief died in 2007.
Japan's greatest-ever racehorse Deep Impact, foaled in 2002, won seven Japanese Domestic Grade One races, including all of the races of the Japanese Triple Crown before retiring in 2006.
The horse earned around £7m (€9.7m) in prize money and, now put out to stud, has been valued at around £24m (€33m).
He came from splendid pedigree. His sire, Sunday Silence, single-handedly reconfigured the stagnant Japanese bloodstock industry.
His dam, Wind In Her Hair, was herself a Group One winner from the bloodline of Highclere.