Well here is the elephant in the room.

Setting the prices at this high point will encourage alot of stress on FC members to generate as much gil as they possibly can, leading to some less than kosher ways of obtaining gil. (Botting , RMT, economy manipulation)

Before you had individuals doing this now you may have whole FC manipulating the market/ in game economy so that they can afford to buy the big plot of land. For those that don't think that was possible remember the tier 4 materia / fleece debacle in 1.0?

If they are hoping to decrease inflation on the market boards, they may find they actually accomplish the opposite at least in the short term.