Kewl - found my old explanation - http://wow.allakhazam.com/forum.html?forum=69&mid=1241012876276015203&num=8&page=1
I think this is actually a throwback to the days when the specialty tailoring cloth gear and bags really were uber, but let's go through all possible reasons to think it out.
30m buff - is nice, but hardly uber enough that the cloth needs a 4 day CD or even a 1 day CD - half the time I'm running misc errands when I get the buffs and dont even get to exploit them. If Blizz thought they were that great then Blizz could classify them as combat potions and resolve any issues with exploiting.
Need to slow down bag production - hardly - tailors can make 20 slot bags without issue - an extra 8 slots per player or 10 slots per bank is not a game breaker, heck, the reality is that even a packrat like me doesn't need four 22 slotters - I'm doing fine with 20s.
Need to slow specialty bag production - even less valid - enchanting bags are the most expensive tradeskill bags in the game to make right now - mining, engineering, LW, JC and even the new quivers/ammo-pouches are no where near the cost to make. Same with soul shard bags - a quiver/ammo-pouch gives a better benefit yet is cheaper. So if there's no need to limit production of the other tradeskills and hunters then why limit production of chanter bags and locks?
Tailors can skill up off of cloth - ok, this borders on being a valid reason as the specialty cloths are the cheapest thing to make at their respective skill levels, but then that could be simply solved by narrowing the range of skill ups or removing them all together.
Tailors can skill up off of chanting bags - cost of mats for a chanting bag is certainly cheaper then other tradeskills for the last 10 points (albiet, JC have it cheapest to my knowledge in that cutting meta gems can take you to 450) but once again, if Blizz just wants them to use frozen orbs like everyone else then change the skill level of the chanting bags.
Flying carpets - the specialty carpets have not been introduced yet - if they can be used by anyone then that could be a possible reason but then again, the engineering bike can too and the titansteel CD is only 24 hours.
Specialty cloth outfits are uber - my lock tailor wore his frozen shadoweave (he wasn't a raider so no access to T5/6) till at least 78, so I guess yeah, that stuff was uber. My skill isn't high enough to make a complete set of the new elite cloth but looking at armory, its all ranked as 200 level items and the T7 is also ranked 200 so that means that, without hitting a heroic, much less a raid, a tailor can make his own set of T7 ranked gear. Of course, BS and LW can also make 200 level gear too, so that debunks that reason.
Tailoring is cheap - let's see, the ebonweave robe takes 8 peices and if you're shadow spec, then you get 2 per combine, meaning 4 combines total, meaning 4 imbued netherweave. Frostweave is going for a 10g a stack so that's 20g for the cloth, 6g each for the shadow so 24g and 5g each for the dust so 40g. Toss in 6 more bolts of imbued for 30g for the cloth and 60g for the dust. Frozen orb will be ignored since both sides need it.
So to make a T7 tailor chest peice costs 174g plus a frozen orb - this is buying it all from the AH - time to make = 12 days for a 200 level item.
And now we hit apples to oranges because smiths cant make titansteel chests. >_<
OK, so let's go with the shield - that seems to be on par. Titansteel shield takes 4 saronite bars averaging 2g each for 8g. Titan steel bars AH for 115g each so let's take our time and make em - 3 titanium bars at 15g/bar = 45g, 1 earth at 5g, 1 shadow at 6g, 1 fire at 27g - so 83g each to make ourselves and we need three.
As such, a smith can make a 200 level (thus T7 grade) shield for 260g plus a frozen orb, again, buying it all from the AH - time to make = 2 days.
We've now debunked the concept of it being cheaper - I used the ebonweave peice, which is the cheapest to make of tailoring specialties and its only 100g cheaper, but takes 10 more days to make, so the lower cost does not justify the longer time it takes.
That really only leaves one logical reason why Blizz gave tailor specialty cloths such a long CD - they traditionally gave us a CD and didn't think things through and realize that it isn't justified this time around.
As such, there's no justified reason for a 4 day CD (although I thought it was three days?).
The costs are obviously a bit dated but the annalysis is still valid I think.