From Megan on FoU:
"We don't always produce the full edition for every item. With Barad Dur we made the first 750, the last of which took quite a while to sell. Because of the value of these items, and the sheer amount of space (and cost) they would take to store in our warehouses, Tim opted to discontinue making Barad Dur - which is why it was listed as sold out on the website. While we didn't expect we would got back into production, the full edition was not created so the moulds for BD were not destroyed. We are happy that these last pieces will now be available to those who missed out the first time around."
Seems reasonable to me.