Its not a money pit when the arena is in use at least 50% percent of the year. Any building is a gamble but you hope it starts a chain reaction. Staples Center changed the entire face of downtown Los Angeles which was the armpit of the city, now its a huge huge destination. Not just Staples but LA Live and the entire 10 mile radius. The old adage is: if you build it they will come. A new arena, and hopefully a better product on the court- could cause new restaurants, bars, clubs, shopping/retail, condos, etc to pop up. Now locals have something to feel good about and a new destination.. which means they're spending money. Of course they'll have to do renovations and keep the building updated. That's a given. Staples is the model of what could happen. It does help that they have 4 teams playing in the building..Sacramento wants to do the same thing with their downtown area with a new arena. they're studying the staples blueprint.
On the flipside I see the Sprint Center in Kansas City still doesn't have a permanent tenant. But they never never had a NBA, NHL or a big time D1 college basketball team to begin with. its definitely a gamble, nothing is guaranteed. But I've seen first hand at what a new downtown arena can do for a city.