All good points. But owning an professional sport franchise is not a normal business or ownership proposition. For the billionaire owners, making money is not the most important part. If Steve Ballmer, Dan Gilbert or Joe Lacob wanted to make more money there are plenty of other potential places for them to invest. Owning an NBA team is similar to owning a yacht, 100 million dollar house or Damien Hearst sculpture than it is to investing in a conventional business. The only people that they need to convince their team is worth 4 billion dollars is another billionaire with a desire to own one of the biggest vanity chips a billionaire can own.

The bubble only pops if they start loosing money or realize the other billionaire don’t care about sports teams anymore.