I've organised music events (when I was younger) and community events more recently, ranging from attendance in the hundreds to thousands (low end thousands though).

I just can't see TF being a big enough draw to be worth it, even as a tax write-off.

I've seen a well-funded Star Wars event, run during the prime of the prequels, with BIG-NAME guests, fail to hit 50 attendees. This was also well publicised.

I think you'd be much better off just organising something at a town hall, but again, you're stuck with the issue of content.

Why should people go to this event, as opposed to discussing things online for free? What are the attractions? What can you offer?

Even at Supanova, TF events haven't done all that well, from my observations.