Actually, Batman is not a good example- that stuff 
has been getting out- I'm finding you can get cels 
from BTAS, AB&R and BB for around $50 each, I 
know, I have some. 
For the most part, I don't bother with American 
cels- not just because of price, but I think most 
american animation sucks with a few exceptions 
(Timm and Dini, the recent CN stuff, and Iron 
Giant)
Blair