Seeing the market boards lately, it is starting to look like too many people are viewing the "Asking Price" (aka vendor buyback) as the suggested price.
People putting up stacks of items for 1 gil each does nothing but hurt the economy. It does nothing more then remove gil and ultimately, lowering the price of everything.
1) Take the recent sales (drop the lowest and highest few, like 4 low and 2 high) and make that the "asking price"? This would create more stable pricing over a few days instead of a few minutes as it is now.
2) Posting fees. While I really like not having posting fees, I don't think penalizing someone for posting something that isn't going to sell is fair. The price adjustment part needs to however be somewhat controlled. I suggest keeping the no initial posting fee, but fees are imposed for removing an item or changing the price within a certain amount of time (3 days real time seems appropriate.) After the 3 days of posting, the seller is free to remove or change the listing as they see fit before another 3 day lockout is imposed.
3) This goes along with the first one and remove the ability to look up current prices at the retainer screen. If someone wants to really play the market, let them go back and forth and make sure they are undercutting by the amount they wish. Most of the people will go off the latest trend of suggestion 1 and would create a much less volatile economy.
Whatever is being worked on or thought of doing needs to happen quickly, the way the markets are currently only in a way encourage RMT due to time invested vs possible gains. I get the whispers all the time, I know the gil value of what is basically a hours worth of minimum wage work is in the states... I have also played the game since launch, I know what you can currently obtain in a hours worth of work and it doesn't even come close to what is being offered. I can see were the temptation is.