Where to buy the cheapest?

I've got factions, but am thinking about getting the other two.
I thought eBay would be a good choice, but I guess not.

So who's got the best prices for Prophecies and/or Nightfall?

I dunno, shop around. Just make sure it is a new game, not a used one.

With that being said, i woudn't recommend getting it from Ebay,since most of those are opened and very likely that you will get scammed there.

Amazon.com is a place that you can shop around and find a good price on them. Just be sure that the item is new, not used. I always buy from the sponsored Amazon sellers, since Amazon will guarantee the item and will refund if it isn't what you ordered.

Play.com is awsome got all mine from there really cheap and fast delievery.

I have heard good things about this site before, only bad thing is they can only ship to certain countries (think its within EU they can ship).

I can't tell u who has the best price, but buying it from the official store is out of the question the prices r higher than any you will find in a store. The only exception to this is if you play GW only in PvP. Then getting the PvP editions is an option you might want to consider. As said before, Amazon is a good place to buy it since they have decent prices.

In the Netherlands:
I've seen Prophecies for 20 euro once (still blame myself for bot buying it).
I've seen multiple copies for around 30 euro's recently.
NF is still around 40 euro's in cheap stores.

I just ordered Prophecies from Amazon market place for 25$ (including shipping). It is supposed to be new.