When I sell my cels (which I hardly ever do...I 
cant bare to part with them usually)
I always add what I actually paid for the cel, ie, 
what it cost me to pay for shipping and such.

Like say, one of my cels I got from Yahoo Japan 
for 1000 yen. However after paying all the 
shipping, it certainly didnt cost me $10 if I ever 
was to sell that cel, I'd sell it or ATTEMPT to 
sell it at somewhere near what it cost me.