Not every con pays for the accommodations of every guest. And even if those guests are being paid for, they are giving up their time to be in attendance. As individuals, they are free to charge whatever they think is fair for whatever–and you as a consumer are free to choose to pay that price or to forgo.

The people paying to attend the convention are paying for just that–to attend the convention. And often, the folks who would like an autograph or a photo or a sketch or whatever aren’t people who are supporting their projects–they’re simply people who like free stuff. Not everybody, of course, but enough of them. All you need to do is to go to eBay to see how many signatures and sketches that were done at conventions are being auctioned off by those they were done for.

So everybody is entitled to charge what they want, and everybody is entitled to partake or not.