I tried looking at a few names I'm familiar with and the pictures are so small, it was futile. Ebay allows huge pictures...a seller really has to go out of their way to resize them so small, so that's a red flag to me.
I have many of these same books signed. These look exactly like mine do. I think everyone of them are authentic. The cost of these are low but most of these are purchased and signed at the book price.
Of the 20 auctions I went to probably 10 of the same book signings at Bookends or Barnes and Noble....etc. There are many people at these signings who buy multiple books. Some I've seen buy 10 of everything probably to resell I'm sure.