[Xelaeon]

It's called the law of supply and demand. You flood the market with product and the market price goes down. It is inevitable.

To add on to your point, demand in FFXIV is either inelastic, or near inelastic. There will be the same group of people buying the same quantity regardless whether the price is high or low. So undercutting is actually not a wise move, unless you are desperate or trying to induce a price crash to kill off the competition.