Patch days are the best time in the game to make gold. There is always a short period of time where the demand for a specific item is excessive and most people don’t prepare until the demand peaks. If you plan for this, you can always make bank.
For patch 4.06, the hot ticket item is going to be Shadowspirit Diamonds. There are 3 new Shadowspirit cuts that will be BiS metas for DPSers. Agile Shadowspirit Diamond (Agility/3% critical damage), Reverberating Shadowspirit Diamond (Strength/3% critical damage), and Burning Shadowspirit Diamond (Intellect/3% critical damage).
The patterns can drop off of any Cataclysm creature and are unbound so if you are lucky enough to get a drop, be sure to post it on the AH at a high price immediately. If you find the pattern within the first 24 hours of the patch release I would recommend posting it around 20k gold.
As for me, I already have about 40 raw Shadowspirit diamonds stocked up. I am not sure whether I plan on selling them raw or scouring the AH for the pattern to see if I can find it for a bargain. If I see a pattern available anywhere under 10k gold I plan on snatching it up immediately and cutting and selling the Shadowspirit diamonds. I expect the raw gems to jump up to around 500g a piece with the cut versions selling for over 1000g.
This post is a little bit late to get you prepared to make buku bucks, but what you can also do is check the price of Obsidium ore, Elementium ore, and uncommon gems. If you have an alchemist and a JC you can prospect the ore to green gems or buy the green gems off the AH and transmute as many Shadowspirit diamonds as you possibly can.
What else did I do to prepare for the patch? I bought well over 200 volatile life at a cheap price as I expect an increase in demand as flasks require more of them and new Alchemist trinkets are coming out which require 50 of them to be made.
Enchanters have the opportunity to make money off of some new bracer enchants. Enchanting mat prices will possibly increase slightly and anyone to find the lucky enchanting pattern will have the chance to make a fortune.
Rare gems will also see a slight increase in demand as many of the crafted pieces will have empty sockets in them as you log on. Everyone who is sporting a crafted epic is going to be looking for a gem to fill it with. Inferno Ruby’s could possibly rise in price to around 200g for a short stint.
Next patch I’ll be sure to remind you much farther in advance what to stock up on and how to get rich quick.