Yes, I do think it is fair and ethical if the cel
is worth that much at the time you decide to sell
it.  Just consider yourself 'lucky'.  Initially,
it wasn't purchased for resale, but if the price
was right, why not?

Nothing mroe than a simple supply and demand.  We
(or at least most of us) live in a capitalistic
society.  I one time managed to buy some cels for
$1.76 each.  3 months later, one of them sold for
$65.00 on Ebay.  So I based the rest of the cels
from that sequence according to how much it sold
for and they sold.  Do I feel guilty for not
turning around and selling it for $1.50?  No. 
That is just how it was.  I know some people might
slam me for this and think I am "evil" (no puns
intended Evil Lady!), but if people are willing to
pay that much for it, why would it be wrong to
sell it for that much?

Back in 1929, the first comic book issued (Action
Comics #1) cost $0.10.  Today, it is valued at
around $175,000.  So, if you owned that comic,
would you sell it for $0.10 since that was the
price you paid for it 75 years ago??  I mean, that
would be 'fair' tot he buyer, right??

Star Phoenix