Walking Dead comics books from Image have been on fire, help by the incredible popularity of the tv show. High grade copies are the issues to own, with the CGC census showing over 300 in CGC 9.8 and a handful in CGC 9.9. The comic book series started in 2003 and the popularity is greater than ever.
The last sale of a Walking Dead CGC 9.9 was for $7,000 in May of 2012. CGC 9.8 copies have been selling for over $1,000. Even CGC 9.4′s have been bringing upwards of $500.
Because of the number of high grade copies, I would recommend sticking to CGC 9.4 and better copies.
If you want to find out how to get these comics for a discount, make sure to check out the discount comic buying post.