I undercut the price of Venomous Claw by 5,000g yesterday because I wanted the gil, and 5,000g is a small price to pay to have it now rather than in five hours time. If I really don't care for what my gil is doing at the moment, I'd have put it up for the full 250k and waited it out. Fact is I wanted it now to suppliment buying a Neptune's Staff.
It's not like it hurts anyone in the process. Putting my Claw up for 245k didn't put theirs up for 244k. They make the choice to lower the price further. They could wait the extra hour that I didn't want to wait and sell theirs for 5k more. Congrats to them, I could farm 50 times that in an hour I expect. I cringe when people lower the price something's been at for eight months by 10k, but I understand why they'd do it.
"Hey, I just got an Angel Skin, I don't want to wait 4 weeks for my gil though, so I'll put it down for 10k less to get it faster =)".
It's an understandable logic, for sure. Take a look at Angel Skins on Garuda right now. The market's broken because of undercutters. They got their gil before others get theirs. Good job to them I say.
I'm sorry, I'm a reasonable person with plenty of respect for my fellow players, but this is just a big deal about nothing. I'll continue to undercut people as well, because I want my gil now! That's just how it works!
Sure, it's annoying, but it's part of an economy.