It ruins the Market drastically!!!

I use to sell emperor fish 35k per fish for 2 weeks, I give someone the tip; emperor fish are now 7k a fish and flooded with fish!!!
I tried other methods but people are so desperate to decrease price for quick sell!!!
Ex:
I finally converted 47 gear to Vit IV materia. Sells for 400k. I sold mne for 390k. For some miraculous reason, several players were thinking "Ohh no, Hinamu is selling this 10k cheaper. We better start selling them even cheaper!!" The next day it didn't sell and the prices dropped astronomically to 120k!!!! I know you people want to sell first but stop dropping prices to make the item almost worthless!!!