That joke is getting so old now...
But yea, players will start farming and selling mats more, whilst not buying anything because they want to save all the gil they can. This will create a very high supply on mats but a very low demand.
Also I don't know about you all but 625mil gil leaving the realm seems like a lot of money considering gil generation is so limited at 50 (Around 1.8k per WP after repairs). There are a lot less low level players in the game at this point. Funny considering the whole repair cost debacle we had a while back.
