I'm asking because I saw a beautiful one on 
auction, but judging from the image only it just 
looks like a very well-made reproduction cel to 
me, though.

Since I am not familiar with lithographs at all 
and this is really the first time I've seen one 
regarding an anime, I thought I should ask about 
this.

How much are limited edition lithographs worth on 
average and what determines their value?  I think 
there are enough art and collector experts here 
who could provide a good answer.