That was already happening on my medium population server. One of three things is true:

A) Those sellers are selling at a loss, waiting for every one else to give up, so they can then jack up the prices.

B) They have access to herbs at cheaper prices than you do.

C) They have multiple methods of making gold, and make so much in their other "industries" that they can sell glyphs at a loss because it all works out to be a gain in the end. (I've seen math which shows selling even a single DMC for 60g can drop your cost per glyph to just a few silver plus the cost of the parchment. You think 3g is under cost, but for them, it's still way above cost, and therefore profit.)

Although I've been slacking on my banker alt lately trying to level some alts, I still mill hundreds of gold worth of herbs per week (used to be more - kept one gbank full of IotS at all times) - I make enough gold selling off-hands and Snowfall Ink to finance the entire operation. I could sell glyphs at 1c and still be making gold via inscription. Granted, I am not making now what I was before Warden 2.0 came out since I've yet to find good farming sources for the herbs and I tend to loathe self-farming - I'd rather use one of my other maxed professions to make more g/hr and buy the overpriced herbs on the AH. Wonder if I should just buy up all the glyphs in the AH listed for < 4g...hmmm

Time is money.."friend"