Colin William Hulbert ran three businesses from Supercheap car sales in the tropical north Queensland city.
Through his Cash Brokers company, he charged clients up to $990 to facilitate loans with his own business, Channic Pty Ltd, for consumers to buy often-unreliable second hand cars at his own dealership.
Loans were charged at an interest rate of 48 per cent.
Prunella Harris, a mother of seven from the nearby Aboriginal community of Yarrabah, went to Supercheap in 2010 in search of a bigger car for her family, only to find it plagued with problems.
"When I first put in for the car, it wasn’t even driveable on the road, and then it had to get a few things fixed on it," she told the Australia Securities and Investments Commission (ASIC) in recordings obtained by NITV News.
"Then when my eldest son and my mother went and picked it up… there was no fuel in the car to start with, and the radiator kept playing up."
Ms Harris was one of 10 Aboriginal witnesses, who each lost up to $13,000 between 2010-2012, to give evidence against Mr Hulbert in a court case prosecuted by ASIC.
Last September, Mr Hulbert was found to have breached consumer credit laws, and was today ordered to pay $776,000 in fines, plus $420000 in damages and $47,699 in compensation to victims.
'The actions of the respondents in this matter caused some of the most vulnerable consumers in Australian society serious financial harm.'
Kaan Finney, a senior manager in ASIC's financial services enforcement team, says the penalty should serve as a warning to those who prey on Indigenous communities.
"Often Indigenous consumers are unaware of the protections that the law offer them, and unscrupulous people will take advantage of their naiveté," he told NITV News.
"The actions of the respondents in this matter caused some of the most vulnerable consumers in Australian society serious financial harm. This judgement should serve as a warning to other businesses not to contravene consumer protection laws in order to maximise their own profits."
Mr Finney thanked the Indigenous Consumer and Assistance Network (ICAN), who brought the matter to ASIC's attention, as well as the witnesses who spoke out about the misconduct.