We need more ways to make gold in this game.

[Rinsui]

Unbelievable, after 24 pages of reading you still fail to comprehend the predicament in this thread.

The OP questions whether the server will be experiencing a net gain or a net loss, of gil, once players cannot tap into quest rewards anymore.

How this can be misinterpreted as "how to make money on AH", is beyond me.

And the answer to this may be "neither", because barring fixed fees like airship rides and repairs, the system is recursive and self-stabilizing, because
AH taxes are a direct function of the average price levels.
Less gil on the server -> lower price level -> smaller taxes -> less reduction of the overall gil amount without change of fixed influx -> more gil on the server
-> higher price level -> higher taxes -> more reduction of the overall gil amount without change in fixed influx -> less gil on the server (...)