Like it or hate it, the spreading Scourge is altering our world. I think it's having a definite impact on the economy.
The Garona jewelmarket is nearly empty. So is the glyph market. The market's been hot the last ten days, a lot of people buying stuff. So where are the sellers? Well, a lot of the serious traders use level 1 alts to do their auction work and it's basically impossible to keep a banker alt alive in a capital city right now. So the economy is freezing up.
Fortunately my jewelcrafter is a brave level 70 hunter and she's quite happy to fight off the zombie hordes in-between cutting and selling gems. And she's making a lot of money right now, one of the few crafters able to bring goods to market in these troubling times.
Also, rumour has it that Horde zombies can trade with Alliance zombies. That's a significant change, it's normally a real pain to move gold between factions.
Finally, the zombie invasion has one nice advantage: when was the last time you saw a living gold spammer? Thank you, Scourge.