I'd be interested in organising one... I used to regularly organise and run large events that were attended by 4500+ people, so I know a little somthing about event managment and promotion. I guess it wouldnt hurt to do some figures and see what kind of attendance would be expected, that would give an approximate budget to begin with!
Keep in mind though, there's alot more to it than just throwing some enclosures into a room and expecting people to turn up. There's venue hire fee's, public liability insurance, security, sponsors, exhibitors, advertising, informative materials and other infrastructure required to make an "event" a professional and well run EVENT.
Sponsors would be fairly limited in QLD due to our restricted commercial species list, but expanding the show to include aquariums might help bring some of the larger pet stores (that also sell reptiles like childerens pythons, turtles and lizards) on board
Having the sponsors and exhibitors contribute their fee's would help offset the events overall cost, but I still think you wouldnt get away with doing this properly for any less than 20K (just an "off the top of my head" figure, but if anything I would say even more) and you would probably have to have a small but reasonable entry fee (say $10-$15) to ensure you wernt ******* your money up against the wall as an organiser.
But just using the above scenario as an example, do the maths - $20,000 means that you would need roughly 5K worth of sponsor/exhibitor income and 1000 people to attend and pay their $15 per head just to break even.
