The ink traders you find near inscription trainers allow you to buy any lower-level common ink you might need for the price of one current ink. Glyphs take a variety of inks, and if you want to craft one, you're more likely to need ink from some earlier expansion than you are a current ink. In Wrath of the Lich King, we were trading in Ink of the Sea. In Cataclysm, we've been trading in Blackfallow Ink. In Mists of Pandaria, including patch 5.0.4, we'll be trading in Ink of Dreams -- or at least the tooltip at the ink trader would have you believe.
Right now, if you go to an ink trader (for example, Sarana Damir in Stormwind or Sinzi Sparkscribe in Orgrimmar), even though they claim to only want the new Ink of Dreams, you can actually still use Blackfallow Ink. This is a huge deal, and it will soon be fixed.
This could be fixed two ways. First, they could just make a hot-fix that prevented people from using Blackfallow Ink to trade down. In my opinion, this would be the wrong choice. Blackfallow Ink is still the highest level of ink people can acquire right now, and there's going to be a lot of demand for glyphs for the next four weeks since a bunch of new recipes were announced, a bunch of glyphs changed what they do, and people are playing alts. It doesn't make sense to force people to wait until Ink of Dreams is available and affordable to get the glyphs they need.
Of course, people can still farm old zones to directly mill the old inks that people need, but that's not as common as people farming in the current Cataclysm zones.
The other way they could fix this problem is to simply and explicitly allow people to continue trading Blackfallow Ink in for whatever they really need at the ink traders. This would hurt some scribes who spend a lot of time stockpiling inks in preparation for this change, but it would greatly help the average player who is simply blindsided by the price increases on glyphs.
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