James Cummings is hoping he can help turn the best-selling colt at Karaka so far into a guineas winner and a potential stallion.

Cummings, who trains with his legendary grandfather Bart splashed out $NZ600,000 ($A561,508) through their bloodstock agent Duncan Ramage to buy a Fastnet Rock colt out of Dance On By, a sister to top sire High Chaparral.

Cummings said the Waikato Stud offering was an athletic colt bred on a cross that had produced several good stakes winners, and by the same sire as Rock Classic, who won the Australian Guineas for the stable.

"Unfortunately a horse like him had to be gelded, but I don't think this horse will be," Cummings said.

"Hopefully this will be a horse that wins a race like that while he's still an entire and then becomes a multi-million dollar stallion."

Cummings, whose grandfather has had great success with horses bought from New Zealand, and Ramage have already bought 11 horses and Cummings said Karaka was proving a good place to buy.

"It's a really good buyer's market. Even though the average was up you saw what the average was doing at the Magic Millions so I think that's just a reflection of the global economy," he said.

"We're able to swing from the shoulders at Karaka and it wasn't quite the case at the Magic Millions."

Only one other horse sale had hit the half million mark - a High Chaparral filly from the family of Atlantic Jewel sold for $500,000 to Sir Owen Glenn - though Cambridge Stud turned down a $580,000 bid for a Fastnet Rock-Diamond Smile filly.