I have three characters each with three retainers all selling assorted stuff. I price check every day or three.

I don't worry about the 1 gil undercuts a bit, not only do many think about the taxes, many also buy the 1 gil more one due to disliking the 1 gil undercuters.

The ones that bug me are those who seem determined to crash the price. Like undercutting by 20 - 30%. I remember one item that went from 150ish gil to 30something gil in less than a week. It wasn't a high turnover item, a hammer of some type, and none sold in that period of time. I did manage to sell mine though so all's well that ends.

On the gathering sales side, if people put HQ endgame gathering stuff up cheap I will buy it and resell at a higher price. Hand me free gill and I will take it.

Its a game, don't worry.