You're missing the whole point of that book then.
The whole Millionaire series was a compilation of data gathered over several years by Thomas Stanley and his associates. The premise of their first book The Millionaire Next Door was based on just the fact that most millionaires are not what you would expect them to be (ie: 'Ballers'). On the contrary, they are more conservative in their purchasing habits, many run their own business in less-than glamorous industries, they don't dress too hip, drive baller cars, a surprisingly low percentage of them are in the typically expected professions (Doctors, Lawyers, Corporate Execs).
Go read The Millionaire Next Door first, then come back to The Millionaire Mind.