I would say it depends on the cover. You're looking at a minimum of 1.5-2K most likely, closer to 3-4K for one with zombies. The covers to issues 1-6 are not on the market and currently still in Tony's collection. I believe #19 is for sale for 4K, and most of the rest of his covers are already tucked away in private collections. Personally, I got a sweet deal on this #7 cover
http://www.comicartfans.com/GalleryPiece.asp?Piece=371863&GSub=54386
Went through this whole thread again. Just a reminder of what the prices used to be.