Sure, other items can have a higher value because 
they are hard to find. I am just saying that 
limited edition cels are 1) hand painted 2) 
produced in very limited quantity 3) each copies 
of them need a lot of work.
So they may not be the same as a production cel 
but they are certainly more valuable than a 
poster.

Promotional posters, lithography or whatever else 
are mass produced (even if in small quantity) and 
there isn't more work involved in producing 1 or 
producing 10000.

I am sorry but I don't think that you can compare 
those two kind of produces.

> items, but not for all. I currently have been 
> able to get 3 of the 4 "promotional" posters for 
> the anime I collect and they can be pricey and 
> hard to come by.

Humm... the only reason they are hard to find is 
because they were released long ago. (and not 
because there is only a small quantity).
And the only reason they are expensive is because 
you don't buy them from a second-hand shop in 
Japan. (where they aren't worth much)

Promo posters are _given_ to customers in shops.
They are printed in large quantity. It's only when 
they are old that they may be harder to find.

Cheers,
Yann Stettler