Oh yeah, I had forgotten about this. The wands you need for the Hallow's End Achievement The Masquerade are not limited duration. I had saved mine from last year, so immediately when the event started this year I was able to post "Selling wand charges for the Masquerade, X,X,X,X for 20g each."
I probably have about 5-10 wands on most of my 30 toons, and I've probably sold about 400 gold worth of charges so far, just in the course of continent hopping thru Dalaran while doing Hallow's End quests.
I'm not gold hungry, otherwise I could just stay in Dalaran and constantly spam trade with it. If you wanted to do so, the first few days would be your best market, as the demand will definitely wane.