Just curious....
Have you asked them what THEIR budget is?
THEIR budget, not yoursis your starting point.
Quite often organizations will dangle the carrot of "exposure to new customers" as an incentive to bring your price down and/or almost work for free. I promise you that you will get very little business from an event like this. You need to find out what they can spend on dessert, and then see what you can do to make something for them AT A PROFIT. It's a business summit. They'll understand if you tell them you can't work profitably within their budget.
It's also ok to walk away from business opportunities if they simply don't make sense financially. Remember.... Your business isn't a charity. You have bills to pay just like every other business, and in fact handing opportunities like this to your competitors is a good thing in some ways. Let THEM work for free!
Cheers
Brad