It's called "good business sense". Admittedly, a 
lot of dealers do this out of love for the medium. 
I would guess that most of the online sites are run 
by fans who just want to add to their personal 
collections. Keep in mind that even dealers like 
Yann and Parallax are probably not charging what 
they originally paid for the cels either. Buying 
and reselling goods for a profit is what business 
is all about. It may not seem fair but that's just 
the way it is. I'm sure that none of you would turn 
down the chance to make a profit on one of your 
cels if the price was right. The proof is in seeing 
weather or not the cels actually sell at the 
inflated price.