I think Ebay might be the cheapest too but you have to be carefully who the seller is...check out the seller's rating
ebay is good but not all item are genuine, yesasia would be my best choice as they have alot or rare drama's and movies.
+1 for YesAsia, I usually buy my music from there because they have free delivery and I won't get hit with any import tax...
I agree with most of the comments here. ebay for cheap probably bootleg DVD. Yesasia for hardcore collectors.