For me, it is purely about price. I am willing to 
plunk down a little extra for a cel with a nice 
matching sketch. However, if it is a really hard 
to find cel or a wishlist cel, I'll still pay 
extra even without the sketch. For cels from AIC 
or from Miyazaki anime, it means something more. 
If you have a cel from Kiki's Delivery Service 
with a matching sketch, it can jump the price up 
at least $100.