Interesting strategy these guys have going. Look at these price histories.
http://www.ffxiah.com/player.php?id=1467538
http://www.ffxiah.com/player.php?id=1467545
http://www.ffxiah.com/player.php?id=1467546
All buying and selling the same items for very low prices, buying others' items at these prices then jacking it back up to make profit for this guy:
http://www.ffxiah.com/player.php?id=1467249
So just a note if you see people like this selling items really cheap suddenly, try to take advantage of them if looking to buy, or if you're trying to sell, don't fall for their tricks, because the market will recover on its own.