Are all BTN stupid or is it just on my server?

[DPZ2]

In a video game though there's no pressing need to get it sold now (unless maybe you're really tight on inventory slots), so selling at a loss doesn't make much sense.

This is your first mistake, to believe that someone who undercuts greatly is selling at a loss.

No, they are selling at what they want to receive at a price that will be more attractive to a buyer. You may consider them misguided, they may be frustrating to those who want to max out the gil counter, but they are not selling at a loss.

This is not work. If you approach an MMO expecting to be amply rewarded for your effort beyond what other people think that reward should be, disappointment and frustration will follow.