Poison pill undercutting is a tactic that I'm really of two minds. Typically, it involves a seller aggressively undercutting to drive the prices of all glyphs to a point where it's no longer profitable. This usually goes on for about a week or until the seller runs out of resources. The idea is to discourage and drive out the new sellers from the market.

Does it work? I've seen it happen several times on my realm, and sometimes it works. But here's the thing. It absolutely will not work against the established competitors, and an angry competitor should not be taken lightly. You can expect some of them to take it personally and don't be surprised if you suddenly have a vendetta on your head.

As for new sellers, you may discourage a few, but they are like an army of ants marching relentlessly into the market. The ones you discourage will be quickly replaced, especially after articles like this one. At the end of the day, poison pill undercutting has very short term benefits, but in the long run, it's unsustainable and in a very competitive realm can have unexpected dire consequences.

I envy your server having glyph prices high enough to undercut by 10g. Most of my server's glyphs have been below 5g for weeks. Even the highest prices hover around 15g, and rarely for long.