Actually the more I think about this, the more ludicrous it becomes. I think you're high by a factor of at least 100, and maybe quite a bit more than that.
75,000 attendees times $350 a pop = total ticket revenue of about $26 million. They have of course collected most of this already through the presale, but let's keep it at $26 million just to humor you.
Current yields on short term treasuries are well under 1%. bankrate.com is showing 1 year treasures at .14%. Note that's not 14%, no, that is 0.14%. But to humor you I'll use a full 1% APR, which is much higher than what GV can get.
$26 million times 1% divided by 52 (weeks in a year) equals $5000.
but if we use more realistic assumptions.. say they've collected half the cash already through presales, and can only get treasury rates..
$13 million times .14% divided by 52 equals ... are you ready? ... $350. Which makes you 214 times higher than that figure.
edit: yes I have excluded hotel revenues from this because "they" (GV) don't actually own hotels or anything.
In short, 'your estimations' are fucking stupid, and you should go fuck yourself.