Glyphs can be mass produced with high markup and low costs. The cost to list them in the AH is nothing. When you mill a stack of herbs you get 2 different types of ink from it. One ink (Ink of the Sea) goes into the glyphs or can be converted 10 at a time into that other ink (Snowfall Ink). The other ink is used to make darkmoon decks.
Lets get some numbers to work with:
20x[Adder's Tongue] => 1x[Snowfall Ink] + 6x[Ink of the Sea]
10x[Ink of the Sea] => 1x[Snowfall Ink]
Here is the math behind [Snowfall Ink]. If the cost of your snowfall is too close to your adder's cost then you can alreay make a profit by milling. I am going to scale up the example to make the math simpler.
200x[Adder's Tongue] =>10x[Snowfall Ink] + 60x[Ink of the Sea]
We can convert that 60 ink of the sea into 6 more snowfall ink. If 10 stacks of adders costs less then 16 snowfall ink, you could make a fair amount of gold just buying/milling/inking. That's one way JC makes gold. Buying/prospecting/crafting/DEing everything for a profit.
Lest move on to glyphs. Ink of the Sea can be exchanged for any ink needed to make a glyph. The most your glyph will ever cost is 2x[Ink of the Sea] + .50 silver parchment.
(20x[Adder's Tongue] - 1x[Snowfall Ink] ) / 6 = cost of 1x[Ink of the Sea]
You can see that Ink of the sea can be produced for dirt cheap. Most of the cost is the time spent milling it. If you move to a large scale, make sure you have the market for that much snowfall. The larger numbers I produced, the harder it was for me to unload snowfall and the price keeps falling.
Someone making 100 glyphs a day only has to sell one stack of snowfall a day. Someone making 300-400 a day has to sell 3-4 stacks a day.
That brings us to Darkmoon Cards.
I don't like to deal with them but here is what I know. When making darkmoon cards you have a random chance to make one of 4 types of cards that can be numbred from ace to eight. I did say random. The math says that on average for every 32 cards you make, you should have enough cards to make 4 decks. You will have lots of duplicates but should have enough of the cards of the type you need for a deck, but you may have to do some trading.
6x[Snowfall Ink] + 3x[Eternal Life] + 3x[Ink of the Sea] => 1x[Random Darkmoon Card]
192x[Snowfall Ink] + 96x[Eternal Life] + 96x[Ink of the Sea] => 32x[Random Darkmoon Card] => 4x[Different Darkmoon Decks]
You may do the math and figure out that making cards with the extra snowfall is better then selling it. If you have no market for snowfalls, this is your only option to unload them
Cards and Glyphs work well together. They use different parts of the same plant. If you don't want to get into the other market, try to team up with someone that does work it.