Well, I don't know about everyone else, but 
personally, when it comes to needing money to get 
cels..I work for a living. ^-^;;
I can certainly understand that in the 
progression of getting newer and better cels, 
it's not a bad practice to sell of the older 
ones.  But I really don't think it's the case 
when someone purchases them, and turns around to 
sell them immediately.
I think you've already seen that people don't 
really appreciate the practices, and it's already 
been mentioned that doing such drives cel prices 
up even higher..  
I first noticed all this when I saw Ryuu Knight 
cels listed..  I'm a fan of the show, and a 
collector, so I went over to see which they 
were..  I immediately recognized all the cels as 
having come from a lot on eBay (I can't remember 
the final price, though I know it was less than 
$20 for all 6) going for $10 each.  I was 
especially disappointed, since I personally know 
the original seller of the cels--he'd offered 
them to be before at $2-4 per cel before he put 
them up on eBay, and I know that he really 
disapproves of dealers marking up prices.  
Frankly, I didn't even look at anything else on 
the page after seeing that.
While I'm sure you've gotten the point by now, 
I'd like to reiterate--you're losing a lot of 
potential future customers with this practice.  
There are many easier ways to make some extra 
cash that don't involve ticking off the people 
you're trying to sell to. ^-^;;  I'm sure you 
didn't mean any harm by it, but it's the sort of 
practice that gets people off to a very bad 
start..

~Mala
(who is very happy to have her computer back up 
and in working order, after several days of being 
lost to the internet-world)