Having a rich owner is good for the fans, because the owner is willing to pay for a winning team.
Sometimes they're willing and sometimes they're not. Often times a losing team is more profitable. Joe Robbie built one of the best football teams ever, but he was relatively poor. You are right that it takes a commitment from the owner to having a winning team.
The problem is when you have only four or five teams with rich owners, and it squeezes out the smaller teams. A Luxury Tax is nothing to a guy like Ballmer.