"It's amazing that dreams can come true," McDonald told Tony Veitch on Newstalk ZB. "I always hoped I would be good at what I do. I travel round the world every year and do what I like to do."
McDonald rides for the Godolphin Racing stable, the massive private operation of the Sheikh Mohammed bin Rashid Al Maktoum and his family. The Sheikh, who has an estimated net worth of between US$12-18 billion ($16-25 billion), is the Emir of Dubai and vice president of the United Arab Emirates. He owns Emirates Airlines, built the Burj Khalifa and is mad about thoroughbred racing.
Godolphin has an estimated 2,500 horses worldwide, with stables in Ireland, England, France, United States and Australia.
And McDonald is their contracted rider in the southern hemisphere, on their best horses for all the big races in the Australian spring. He's also raced extensively in England, as well as the USA and Hong Kong.
"He's got stables everywhere," said McDonald. "It's a really good situation. I can just hop on a plane, travel to America for the weekend and ride."
"What James has achieved is quite remarkable," said racing writer Michael Guerin. "It's hard to compare with anything else...it's a bit like Scott Dixon suddenly getting a Formula One drive, it's that big. He's already in the top five jockeys in Australia and could go on to be the best rider this country has produced.
It's been a steep rise for the Cambridge born-McDonald. Less than a decade ago he was an apprentice, rising at 4am every morning for track work before racing at modest events around New Zealand for small purses.
He moved to Sydney in 2012, hoping to make it big. Within two years he had won two of Australia's biggest races - the Golden Slipper and the Queen Elizabeth Stakes - as well as topping the Sydney riders Premiership. Then followed the offer to ride for the Sheikh.
"It was pretty nerve wracking but it started quite casual, I was only riding for them now and again," said McDonald. "They demand perfection, but I am privileged to be involved in what they have and all [of my horses] are going to be fancied runners. "
Industry sources estimate McDonald's earnings to be anywhere between $1 and $2 million per year, depending on results. But there are significant sacrifices.
"Getting to the weight is a big battle," said McDonald. "I'm naturally 60 kilos and I am riding at 54 kilos. There is nothing on me left to lose. When I am riding I'm pretty much down to the bone and I am trying to control a half tonne of horse."
Before a race meeting like yesterday's Cox Plate, McDonald needs to drop six kilos in 48 hours.
"I'll have lots of veges, a bit of protein, cut the water intake, restrict fluids - that is what I am wasting out," said McDonald. "Then go for a run, put the sauna suit on - it sounds a bit daunting but that is what I have got to do."
