Because people only have so much disposable income.
You think 2500 people a game wouldn't be a big deal?
2500 people x 41 home games = over the course of a season.
102500 empty seats x (at a minimum) $8 seats = minimum $820,000/yr loss
In all actually, you're talking about on average a $30 ticket in the SBC,
so 102500 x 30 = 3.1 million.
And that's not factoring in concessions, parking, and merchandising.
The real kicker though will be the corporate sponsorship, which is where the Spurs cash in on group ticket sales and luxury boxes
Just because TheWriter has moved on from bridges and southside highways to something that could potentially boot the Spurs out of San Antonio doesn't mean the numbers change.
For perspective, floor seats for the Saints @ $110.
$110 x 8 = $880.
Nosebleed seats for the Spurs this year, season ticket package of 45 games (regular season + exhibition), at the $20 level, comes out to $915.75 (per season ticket information I have in my possession).
So right there, for $30 cheaper, you went from nosebleed seats at the SBC to lower level field level seating at the Alamodome (using this year's prices as a model).
And you think that won't impact things? Keep dreaming.