I suspect most millionaires don't own private jets because they don't need them and probably cannot afford them: cost of plane, pilot, storage, fuel, maintenance, taxes, insurance, etc. I bet all of that is an order of magnitude compared to a car, even your typical luxury car. Billionaires are more likely to have them but probably not all.
But Sampson was talking about the Houston basketball program, not himself personally. That's a different situation altogether. His need for a private plane was specifically professional, for recruiting, and makes perfect sense. He even explained this in the short clip. Even if he could afford one and wanted to pay for it himself, it might be violating ncaa rules.
The issue is more complicated than it might seem.
“Incline my heart to your testimonies, and not to selfish gain!”
Psalm 119:36