One effects of adding the raw material traders in 6.1 is that mats now have a more solid floor under their price. For most mats this means they will go up in price, for others it won't do much (see Enchanting). Another thing this does though, that's possibly more important, is establish relationship prices between mats.
Ore and Herbs
At the time of this post we've seen the fur trader, ore trader and currently have the enchanting trader on US servers. An interesting phenomena has occurred on my server in particular, which doesn't overly surprise me, but leaves me scratching my head. Yesterday on ore's first day the prices shot up from under 1g per piece to over 2g. Even now the price is hovering just under 2g the day after. That is fine and dandy, and more expensive mats means more profit in general so I'm happy to see it. What surprises me though is that herbs have not yet equalized to ore prices.
Knowing how ore behaved yesterday, last night I invested in herbs under 1g, because we know ore and herbs have the same trade in rates (as do all the mats), and logically one can assume (on my server at least) that prices on the first day at the very least will be in the 2g range. I bought as high as 1.5g per last night thinking I'd possibly flip it today if we got herb trader. Of course, we did not, and this morning, not just one, but all herbs were down under 1g again. Hard to know what people think, but considering ore is still hovering around the 2g mark, you'd think they'd put 2 and 2 together that their prices are now tied together. Moreover, what I think this is indicative of is that we can expect sinusoidal oscillations in the pricing of different mats because of these traders, and as a result, keeping good track of the ebb and flow on your own server is going to be key to maximizing profits in the days to come.
Since all mats have the same rate, it is of course advantageous to do trade ins at the cheapest rates possible, which for most will be herbs and ore, but don't overlook the daily quest at a 2 for 1 rate, it makes almost every mat worth it. Even low level 90+ alts can make it to the traders, you just need an invite to a garrison by someone who has a level 3 with the trader. In the past few days I've been easily getting invites through the premade group finder, just search under custom for trader.