Have your cake, but eat it too.

Back in the last days of the lich king
Northrend herbs were plentiful.  Mill, talk to Jessica (who incidentally was where you were hearthed), craft, post.  Addons to help you

• Buy cheap northrend herbs from the AH
• Buy from Jessica.
• Queue glyphs to craft
• AFK Post on the AH and walk away
• AFK undercut
• AFK collect mail

Manually you had to :

• Hearth
• Walk 20 steps to an AH (if you were an engineer/inscriber)
• Walk 10 steps to a mailbox
• Walk 20 steps to Jessica
• Craft the glyphs (one click per type of glyph)
• Walk 20 steps to an AH (again if you were an engineer/inscriber

Ok there was a bit more to the manual portion but not much.  Everyone was doing this on thin profit margins.  Costs of 2g50, sales of 5g were common.

But then things got harder.
All the changes were talked about on the patch notes or on the bloggosphere.  If you missed it, you missed out.

• Glyphs needing 3 inks instead of 1.  I made 40 of each glyph before this dropped ca ching, but if you didn't you were behind the leaders.
• Patch 4 came earlier than I thought, and had installation issues for some.  Great if you were on first and/or pre-loaded the AH. oops :  I didnt get all of my glyphs up, and it took 3 days to sort out installation issues.
• Downgrading inks from Blackfallow instead of ink of the sea.  I converted all of my ink of the sea before this ca ching.  Otherwise you had to now mill old world herbs
• Some glyphs could no longer be crafted.  I still had large reserves ca ching.
• Some glyphs were introduced later, and you had to learn them. oops - I missed a few days but oh well.
• Everone could learn all the glyphs for their class.  For some - gotta catch em all. ca ching (large stockpiles)
• A very large distraction happened - people wanted to level again.

People got out of the habit of regularly crafting glyphs.  We had large stockpiles, and if we needed to craft the odd glyph or two, no problems.  

But now, the stockpiles are running low.  We are back at work.  I think northern hemisphere kids are alredy back at school.  Soon Australian kids will be back too.  There are still dungeons to run, rep to grind, raid bosses to dream about.  And glyph making became hard.

The unprepared/unwilling were already knocked about by the changes up to 4.0.  The semi-prepared fell in love with their easy stockpiles.

Ca Ching
I have been upbeat on Cata glyphs for a very long time.
Those that are left are not only making more gold, but also more gold/hour than we did before. However, we need processing time and to think about our purchases.

• What herbs do you need for Jadefire ink?  
• There are never enough herbs for Ethereal ink so we need to downgrade via Jessica.  
• Our server is about to have price pressures on Northrend herbs/ink
• Jessica is a pain to get to.
• Do I mill, or do I run a dungeon
• Do I post glyphs in front of a PC or do my real life chores
• What does this glyph cost me to make again?

Each barrier is also a barrier to the competition.  People also didn't learn all their glyphs when they were cheap.  Also people are levelling a lot of alts.  For those that are left the pickings are ripe, but time consuming.

I have increased sales, but I have also have time pressures.  I have the toons and desire to work the prospecting shuffle but at the moment lack ability to prioritise it.  So I choose to

• reorganise my glyphs
• increase my fallback and threshold on glyphs I have 20 or les
• reduce my fallback and threshold on glyphs I have more than 20
• reduced my 'holding' to 15 of each glyphs (down from 20).  (This piper will have to be paid, but maybe later when herb prices drop)
• Re-engage the services of an ink miller

During my (mostly failed) reorganisation attempt, I went AFK from selling a bit (APM how I both love and loathe thee).  Also, while I don't track individual sales closely, I am sure that random glyphs are selling out.  I intend to attempt to re-organise glyphs out of game this weekend.

On our server, Breevok is running low on Northrend herbs.  The unholy trinity of his toons, my toons, and the dark side of the moon have, on the whole, been supplying the market.  While we do not practice active price collaboration, we seem to have fallen into an informal gentlemans agreement about the pricing and undercutting.  And I suspect that we are all better off because of it.

Untill the price of Cataclysm herbs drops significantly, and it wont for several more darkmoon faire's + guild cauldron achievements, the biggest risk I see is that we stop servicing the market, and the market 'demands' a new glyph seller.

With Breevok to keep me honest, I expect there to be cake for a while to come.