I attend a number of events throughout the year for promotional, research and business purposes.
If you would like me to attend your convention, but it's not in my usual circuit, I will be happy to, schedule permitting. For this, I require transportation or mileage, a basic hotel room and enough per diem for basic sustenance. Alternately, if we can negotiate tables in the dealer/exhibit hall, I'll pay for them and absorb the per diem. Obviously, more generous offers are welcome. I will attempt to do at least two hours of panels a day, and have been known to do as much as six hours a day.
If I am attending your convention, I am always happy to meet with fans and sign autographs. In order to officially be listed, and to participate in programming, I must have a complimentary badge. This should go without saying, but a small number of conventions now expect pros to pay to participate, or offer "discounts" off the standard rate. However, I will not pay for the privilege of letting you use my name to draw attendees, and then entertain and educate them. This is not a "loss" for your convention. At most, I will eat a few snacks in the Green Room. If you gain even one additional attendee because of my draw, the convention is ahead. If I have to pay for the badge, I will still attend if it suits me, but I'll attend for my own purposes.