lets talk about undercutters.

[PirateCat]

You guys are seriously over charging people... to the point that they they end up buying gil just to get this stuff. For example the Mog mansion on my server is going for 15+ mil.... The moogle bush is going for 5 to 7 mil.... Other housing items are easily going for 4 to 7 mil. 3.0 Glamour items are going for 900k to 3 mil a piece.

The Mog house item requires multiple items that are gated behind RNG and a significant initial investment (into building airships) to acquire, a couple of different specialist recipes out of classes that make almost nothing else, and the participation of several people to advance the crafting project. Most of the 3.0 glamour items require rare drops from treasure maps - which are a time gated resource; people who sell them are giving up the opportunity to do a map that day in exchange for gil - to make. These things are expensive for a reason. You're free to encourage more people to get into these markets if you want (which makes a difference - on Balmung the glamours are going for maybe a third of what you quoted.)

The demand is so high that item x sells in less than an hour for 120k everytime it is put up. So why does someone think "Oh I'll put 40 (non stackable ones) of them at 8k and therefore destroy any chance of the price ever going up again"?
I mean, even if you have many, what do you gain by undercutting THAT much?

40 items at 8K which reliably sell at 120K within an hour? Sounds like an excellent opportunity to buy them up and make a few million gil reselling them.