I agree with Tabi on this one.  I've bought tons
of cels from AnimeLink and I have no complaints. 
I've gotten great deals from Rick before at really
low prices.  I got my Nahga closeup for about $200
and when I saw it on eBay the reserve was not met
at 300.

Just remember cel collecting is a hobby, and no 
one is forcing you to buy any cel.  Most sites
I've visited have a mix of underpriced and
overpriced cels.  Just pick what you think is
worth it to you.