Just a question-- to what extent should we consider attendance numbers to be an indicator of broad, region-wide support of a team? While it would obviously be stupid to suggest that good attendance isn't an indicator of support, I'd argue that at least a couple of factors can exacerbate decreased attendance for a team in the midst of slump where fair-weather fans have stopped going to games:
Ticket cost
As ticket prices increase and middle class incomes fail to increase accordingly, the set of fans with enough spare money to attend games regularly decreases, perhaps drastically depending on region. Even if we don't make the assumption that a larger portion of wealthier fans are fair-whether (which is what my gut tells me), no matter what way you slice it you're left with the fact that your potential customer base is smaller. Some of this might be mitigated by giveaways and ticket deals that crappy teams put on, but in my mind this is just a small bandaid on top of the larger root problem.
Arena location
If an arena is built in a location that is difficult for your fans to reach, either due to geography or infrastructure, then that will further depress attendance.
Detroit is a good example here. The Pistons play in a wealthy suburb 30 miles north of the city core. When the team is rolling, as they were throughout the 2000's, just about every night is a sellout. Wealthier fair-weather fans in Oakland County flock to the Palace and fans throughout Metro Detroit are willing to make the sometimes > 1 hour trek through rush our traffic to see a game. When the team is crap, the Oakland Country crowd comes out less and fans from further out want to venture out to see the Pistons play the dregs of the Eastern Conference.
On the other hand, if the Pistons played close to the city core, they would be much more centrally located for the vast majority of fans. This would reduce . My argument isn't that John Kuester's Pistons would've been selling out if they played downtown, just that their numbers might be 10%-20% better.
I think Seattle probably dealt with the same issues with Key Arena (I've lived in Seattle for a few years, but after the Sonics already left). While this is a different situation as Key Arena is close to Seattle's city core, the infrastructure of the neighborhood it is in just isn't very ideal for supporting an NBA arena.
Unless you're walking, getting to the arena pretty much means passing through one of the most congested traffic corridors of one of the most congested cities in the US. Additionally, the parking situation is pretty dire as your surrounded by moderately-dense residential, some nightlife, and possibly other events happening at Seattle Center.
Compare this to the SoDo neighborhood, where the proposed new Seattle arena would be built and where the Seahawks, Sounders, and Mariners already play:
I really think that CentryLink's location has played a big role in the impressive attendance numbers the Sounders see. If you work or live in Seattle, it's easy to go see a game on any given night from downtown. If you live in the southern suburbs, you can take the link