"From my perspective, I think it's about attitude and about what you can achieve as a person," he told the Bay of Plenty Times Weekend.
Mr Minnell said he had the smarts to study when he left school but chose to pursue a career as a stock exchange agent instead.
He did well, climbing the industry ladder and up through organisations such as the New Zealand Fire Service and Telecom to run his own businesses such as Tauranga Placemakers and the newly launched Dixon Homes.
Mr Minnell said in his experience having top qualifications did not mean someone could do the actual job. "All it says is they can study," he said.
"Whenever I've been employing, the qualifications come into it but I want to know more about the person and their fit in my business, have they got the ability to do the job?
"But I'm not against people going to university. All my kids have been and I encourage them to do so."
Mr Minnell said benefits of qualifications depended what field people were in.
Doctors with higher qualifications were well recognised but in other fields qualifications meant little, he said.
Meanwhile, Dr McMillan spent seven years studying his doctorate at Waikato University, balancing the education with full-time and part-time work.
"The biggest thing was that it took up a huge chunk of my life and six years into it, I was considering giving it up.
"I was thinking: 'do I really want to do this?' because I felt like I was getting nowhere ... when I did finally finish, I was so relieved to have my life back," Dr McMillan said.
"If you had asked me whether it was worth it immediately after I had finished, I would have said 'no, absolutely not'. But six years down the track, if I could make that choice again, yeah I would say I would have done it again."
Dr McMillan said he earned more than $250,000 in the consultancy business he and his wife ran but that was a gross figure.
He said in some instances it was just as good to have a Master's degree, because a PhD wouldn't put you above anyone else.
"If you study full time for years you can chalk up a lot of debt ... and sometimes it's just a title that will give you no advantage," Dr McMillan said.
The Ministry of Education information was gathered by matching information from Inland Revenue with tertiary qualifications data.
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