The point I'm trying to make is that as the value of gil goes down (due to undercutting, oversupply and under-demand, etc) the average amount of money a player can make per week goes down. However, the prices that NPCs sell things for (repairs, teleports, FC housing) does not adjust with it. So basically what the rampant undercutting is doing is hurting everyone who repairs their gear at an NPC, who uses the aetherytes to teleport, who buys dyes and low-level materials and especially hurts those Free Companies trying to buy a house.

If all of the NPC sell prices were to scale with the relative value of gil based on the market boards, then there'd be no problem. Of course this doesn't happen (it would be far too easy to exploit if it did), so the absurd undercutting and deflation is actively hurting everyone by effectively making everything sold by NPCs cost more.