Dead horse is dead. Yeah, matt prices have fallen, nay plummetted.
On my server, theh hardest hit are Dream Shards. They've gone from 25g to 6g. Dusts are sub 1g and Abyss Crystals go for about 25g.
I'm vendoring green and blue items more often than not these days tbh, whilst keeping a large-ish stockpile of matts (around 300 dusts and 50 dream shards and crystals) on my banker for sale 6 months or so after Cata is out, when I expect prices will jockey up again. And of course, just for kicks and I don't need the gold these days anyhow.