Hi!

   Below is quoted from Asylume Anime.  But, 
aside from the general advice, it depends on 
the person signing (the popularity of the 
person).  If Crispin Freeman signs a Zelgadis 
cel?  who knows...maybe some fan girl would 
pay a lot more for it...

   Most important thing I think is how much *
you* want it...Anyway, read below.  Hope it 
helps.

O_O

"Note on Signatures"


"If an item has a signature from someone 
involved with the making of said item, then we
will offer more for that item.  This amount 
varies depending on who's signature it is & 
what they did for that item.  It is preferred that 
the Manga usually should only have 
signatures of the artist / writer (very rarely are 
they different people)....

....Signatures from american anime industry 
people may REDUCE the value of items - 
especially american voice-actors/actresses."