Does making billions actually make you happy?
Most people probably have a pretty settled answer for whether making billions of pounds in life will buy you happiness, be it yes or no.
But it's unusual for a millionaire to be asking the question.
Rafael Badziag made his money rolling out a successful discount bike firm in Germany.
Yet, compared to the world's elite entrepreneurs, his Raddiscount empire represents only a small fortune.
With his business wheels well in motion, he spent the past six years roaming the globe meeting some of the world's most successful wealth creators.
Rafael has attempted to explain their distinct motivations, shared principles, attitudes and world views in his book The Billion Dollar Secret so he and others can profit from the business masters.
But for those not motivated by global trade expansion, let's cut to the chase: are these exorbitantly wealthy people actually happy?
"This is the question people ask me most," Rafael told ITV News from his Black Forest home near Stuttgart.
"The short answer is yes, but not for the reasons you think of."
Rafael said meeting the billionaires debunked the "two extremes that people usually represent; that 'money makes you happy' or 'these poor billionaires are rich but they're unhappy in their private life'."
But he did find evidence of a personal cost in a life dedicated to generating such great wealth.
"There is a price you have to pay for being so extremely successful in business," he said.
"It means decades of hard work, 24/7, you don't take a vacation, you're envious of your peers who travel the world.
"You don't have time for your family, so you need to have an understanding partner. There are all the sacrifices you have to make in your private life."
The scale of the businesses that ultimately make billions bring with them an enormous weight too.
"There is a lot of responsibility and stress to handling a company of 200,000 people," he said, citing the example of Sergey Galitsky.
The man whose 17,000 Magnit supermarkets across Russia make him the second largest employer in the country after the government admitted to worrying on a daily basis about the fate of his delivery drivers on poorly maintained roads.
"He told me, 'When I wake up I just pray to God there is no message on my phone saying there is another accident.'
"So the huge responsibility comes with working on such a huge scale."
He also says he found the billionaires quite isolated.
"You are actually pretty lonely – not just the platitude it's 'lonely at the top' – but there's nobody around who can understand the problems you face on that level. Your CEO, your employees can understand your problems technically but not emotionally because it's not their money."
This all sounds pressured and miserable.
So why does Rafael believe the billionaires are happy?
Rafael believes the personally traits that helped make them their fortunes, such as outstanding people skills, also set them up to be contented people.
"In order to build a business, you have to be really good in human psychology,” he said. "You have to know how people think and build long-lasting relationships.
"Many billionaires have a circle of people who stay with them through decades, and change with them company to company. Because they can handle people this makes them happier."
Rafael said he found most of the self-made billionaires benefitted from "settled private lives" which brought stability at home "to focus on the business".
And he directly linked their wild success in industry with their sense of contentment.
"They have seen many of their visions realised. This brings them a sense of achievement. And they get a lot of recognition in the industry, and also society."
He said several feel indebted to give something back, particularly those who gain great wealth in the East, and are passionate about advancing the lives of those they employ.
"Philanthropy is a huge part of their lives. Giving back to society. But also because by the time you're making billions through a company, a lot of people depend on you."
He said several wanted to help others because they knew what it was like to be poor.
Mohed Altrad, 2015's World Entrepreneur of the Year, was born in a Syrian desert under a tent and raised by his grandparents before making his fortune in scaffolding.
"He told me he still has the hunger – and the fear of hunger – he developed in childhood."
The biggest surprise to Rafael was the people who have made the most cash were often reluctant to spend it.
"Millionaires know how to make money, but they enjoy more spending it," he said.
"But billionaires are on different emotional level. They enjoy making money much more than spending it. Many don't live lavish lifestyles."
Indian tech giant Narayana Murthy told Rafael he wouldn't feel comfortable splurging money.
"His Infosys firm created 200,000 jobs in India, and more than a million lives benefit from his work. Yet he still lives in the same three-bedroom apartment he always did," Rafael explained.
The billionaire's one confessed passion? "Buying books."
Rafael points to British businessman Peter Hargreaves as the best example of a billionaire who embraces the "simple things in life".
The man who created his investment-fund FTSE 100 firm from scratch and banked £4 billion in the process drives a Toyota Prius and "still goes to the pub with his school friends".
"They never talk about business, they talk about ordinary life," Rafael said.
He said Hargreaves had raised his children to be so aware of not wasting money that they turn off the lights in every room in the house except the one they're in to cut down the electricity bill.
But when Rafael asked him what made him so content it was a world away from high finance - or utility bill savings.
"When I asked him when was he happiest, he said: 'I have a nice garden and one of my greatest enjoyments is digging vegetables for lunch on a Sunday morning.
"Just going out and digging out the vegetables, picking the spouts out of the earth.'"
So with answers like that, why does Rafael think more billionaires don't quit and enjoy the easy life?
"They love the joy of the game of making money too much," he said.
"Money doesn't make you happy generally, it just magnifies your personality," Rafael concluded.
"Money just gives you more choice, and it's up to you if you can handle the choice.
"Some people just can't handle it. But generally, billionaires are happier than the average Joe.
"They just love what they do. They don't need to work. They work just because they love it. And if you love what you do, you're happy."
More on billionaires in the news: