I haven't checked yet, but are the discounts and, er, price hikes actually in effect? I mean, it is actually on Xbox Live, for God's sake. It just shows how April Fool's is blended seamlessly into technology.
Ther rest of the content is actually fairly cheap. I'm not sure if this includes Shiering Isles. Just like Thieves Den, and Mages Tower. The fact they are self-aware enough that horse armor was stupid, then go "hey, it's more expensive" is awesome