Since it's now common knowledge that the "Insane in the Membrane" achievement and title will be becoming a Feat of Strength in Cataclysm, if you happen to have any diamonds or Focus, Protection, or Rapidity Librams, now's the time to sell.
On Daggerspine, I put up 11 diamonds at 500 gold each, and they sold out immediately. I had been carefully hoarding them, intending for at least one of my alts there to get the title, but since my highest toon is 63.....it's not gonna happen. The only chance I'll have to do this would be on Demon Soul, with Bloodshrike, who is my achievement whore anyway. I figure if I can get my Zandalar rep and Bloodsail/Goblin rep locked down, I might have a chance of getting it done even after Cataclysm comes.
If you are going for the title, don't forget that those 3 libram quests reward you with Arcanums, which surprisingly aren't useless, since you can turn them in at Zanza in Zul'Gurub for Zandalar rep.
Some might say that it's price-gouging to charge so much for items, but really, people who are going for all these achievements usually have tons of gold already, and are bored and looking for something to do. You're just helping them circulate currency. hehehe.....
Edit: Apparently you will still be able to get this achievement in Cataclysm, due to the immense QQ-ing of players who didn't relish the rushed grind you would need to get it done before December 7th.