Cels Forum

To answer your questions:

a) Average cel size is 9 x 12 inches, but there are other
different cel sizes which are larger.

b) Cel prices vary a lot, depending the series, availability,
and quality.  You can pay less than 1 buck for low quality cel 
from some unknown TV series.  Or you can pay several or
thousand dollars for some rare and superb quality cels.
There is just no definite price range for cels.  But for
beginnier like you, you should stick with something like
below $25.  It is enough to get you some good cels at this
price range, like the ones from AIC studio (Tenchi Muyo,
El Hazard...etc).

c) Go to http://www-scf.usc.edu/~ckawakam/cels/ 
   You can check out each dealer and compare the prices.