Every recent tier of craftable goods has had something in it that limits the ability to mass produce gear. Chaos Orbs are a perfect example. Before they were made tradable (and sellable on the Auction House), the only way you could get the best quality pre-raid and starter PvP gear was to find someone who had the recipe and the orbs. Chaos Orbs are earned doing 5-mans heroics; that meant that low-level crafting alts wouldn't have the ability to craft these highly sought-after items. When Blizzard made them tradable, there was a huge rush for some people to liquidate the large stocks they had accumulated and been unable to use, as well as an equivalent rush of people looking to stock up because they couldn't farm nearly as many as they needed.
There are two main differences between the old setup and the new Spirit of Harmony: how we get them, and what they are used for.
How we get them
The new Motes and Spirits drop off regular monsters you're probably going kill a lot while questing and leveling. This means that you might have quite a stock of them by the time you hit level 90, and you'll pick them up as quickly as you are out in the world killing normal mobs. Unlike Chaos Orbs, the farther your character progresses, the fewer you'll earn. Once you hit the point where your only upgrades are found in a raid, you'll probably see far fewer of these dropping than someone who is still doing dailies and 5-mans.
If you want one of your primary characters to be able to produce goods based on Motes and Spirits, you might need to take them out into the world and fight things that don't necessarily have much to reward you other than the motes.
What we use them for
First off, the professions are not finished, so the way this looks at release might completely change. That said, Spirit of Harmony looks like it will be a requirement for a much larger number of items than the Chaos Orbs were. In fact, from what I'm seeing here, it'll be impossible to get to 600 skill in at least a couple of professions without them.
Now it's certainly possible that we'll simply get enough to max out at least one profession just by leveling and doing the 5-mans until we're ready to raid; however, it's also possible that it will take more of these than can by generated as a by-product of things we'd be doing anyway, and that means farming in addition to buying tons of materials from the AH.
Especially hard hit will be people with two crafting professions instead of a crafting and farming profession. It might require twice as many Spirits.
It's not a tip -- it's the price of a Spirit of Harmony
One common misconception that people have is that because something is not tradable, it doesn't have a price or a value. If a craftable good I need requires a profession I don't have and a Spirit, I'm going to have to offer a tip to anyone but a friend or guildie to make it for me. That tip is essentially the value of the Spirits I'll be using.
As long as it's not officially tradable, though, people will misunderstand the price. Not all professions will have equally desired crafted goods. Inscription only has a few so far, and they're only usable by a few classes. Engineering could only make guns for others with Chaos Orbs, and engineers got as many orbs per month on average, per engineer, as blacksmiths did. This means that some professions will require a significantly better tip for the use of the Spirits than others.
To a buyer in this situation, this feels strange. They don't see the difference. An orb is a orb, and a Spirit is a Spirit. I guess blacksmiths are just greedier.
I'm willing to bet a friendship bracelet that these Spirits and Motes will eventually become tradable, but until then, it's going to frustrate buyers and sellers of goods that require it. Unless they become tradable relatively quickly in the expansion, there will be a length of time where peoples' primary characters aren't doing as much questing and 5-mans as they used to. This will frustrate buyers as it gets harder and harder to find a crafter who is online and willing to use this scarce resource for a tip. This amounts to having crafted gear (which generally fits into that awkward phase between the quest gear you have when you ding and when you can start doing harder endgame content) become much more rare.
Savvy crafters who want to turn a profit will be able to mitigate this effect a little. To profit from crafting gear when there's a BoP reagent, traders will to collect the AH materials and try to find crafters with recipes willing to use Spirits for a "tip" -- in essence, doing the legwork a end user would have to do and listing the finished gear on the AH so it's available 24/7, regardless of whether the crafter who earned the Spirits in it is online and not busy.
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