Supply and demand. They will have no problem selling a ton at that price.
He made $103 Million in his career. Any player who made more than $100 million is probably going to be pretty expensive to bring in. It's not like the old-timers who actually needed the money to augment their meager earnings from playing before the free agent era.
Unless they've managed their money poorly, most of today's players have no need to sign autographs at shows. Most don't like to do it, and thus, may grudgingly do it-- but I'm sure the going rate will be $150-$250. If people decide not to pay it, then the players won't do it. They're not going to take a lower price because they don't have to. Even if they get $50,000 for a two hour appearance, that's a drop in the bucket when your career earnings are $100 Million +