This is my exact opinion too. Back in the day, it was customary to have the talent sign on the inside first page at the bottom just above all the publishing information. basically because back then it was frowned upon to "Ruin" the cover with a signature. Oh, how times have changed. It was even worse for sportcards back then too. For most people a signature pretty much made the card worthless to collectors.
What I did was I just bought two copies of Fantastic Four Annual #5. Stan Lee Wrote it. One was a CGC 9.2, and the other was a 7.0 signed by Stan Lee. The signed copy I bought on eBay for $200. So here's another caveat. for how much it's going to cost to buy the book you want, and then pay the exorbitant fee from Comicon to stand in line to have him sign it, and then pay a third time to have CGC grade it. Your best bet is probably do what I did and buy one already certified by CGC on eBay. I can almost guarantee, even if the person who sold this to me already owned the comic book, the price to pay to have Stan sign it, and the Price to pay to have CGC certify it probably costed more that what I paid for it.