Do they charge you for those things?
I'm not sure if you're asking about the prices for customers at the conventions, or if you're asking me what they charge me as a dealer.
As a customer, they charge a ticket fee to get into the convention, and most celebrities charge an additional fee for signatures and/or photos. The more popular the celebrity, the higher the fee for signatures and photos.
As a dealer, they charge fees for booth space, (the fees range based on the size of the booth), and some conventions charge additional fees if we need to use their tables. (We bring our own tables if they charge extra for them.)
Many years ago, the celebrities would sign photos or other items for free because their fees were paid by the convention, so they were included with the ticket. That has changed over the years, and now celebrities charge an additional fee for their signature. Some celebrities will only sign specific items, or even photos from specific TV shows and/or movies. Some celebrities will sign anything, but they sometimes charge different prices for different items. It depends on their contract.
Some celebrities are nice and they will sign photos or other items for dealers at no charge, but some celebrities refuse to waive their signature fees for the dealers.