With something like what Ben has, "worth" is not an applicable word. The value of it is whatever Ben were to ascribe to them, not what someone would pay. They are extremely unique items, even if they are unauthorized, and do not hold to the same idea of "whatever someone would pay". It then becomes a matter of whatever the owner would take to part with it.

Ves'Ka, I like your idea of doing The Dark Half. What else would you do with it? Would you have pictures, who would do them if you did? Would you have a ribbon bookmark sewn into the book (never cared for them myself, but many like them)?