Alternate Argument for AH...

[Verecund]

This game doesn't need fees and taxes as "gil sinks"... what it needs are some real long-term commitments / methods of character advancement that can be more quickly achieved in proportion to the amount of gil that is sunk into them. Item collection, item turn-ins, rep grinding items, item enhancement, etc. this game still either doesn't have these "commodities" or just isn't using them ...

[Phenidate]

This game doesn't need fees and taxes as "gil sinks"... what it needs are some real long-term commitments / methods of character advancement that can be more quickly achieved in proportion to the amount of gil that is sunk into them. Item collection, item turn-ins, rep grinding items, item enhancement, etc. this game still either doesn't have these "commodities" or just isn't using them ...

Not sure how I would go about convincing you that small spread out gil sinks are just important as large ones if not more so. About the best I can do is present the fact that just about every MMO has them. (excluding F2P titles which get all kinds of weird stuff with their model)

The issue is apparently important enough to address that it's got a term even (found this out when I was trying to find past mechanics that worked): MUDflation.

Apparently what I suggested in the previous post would be called a Dynamic Money Sink.

Also worth noting are the two examples given; which happen to be the most prominent titles presently, WOW for playerbase and EVE for its notable player driven economy. Both frequently make headlines...

World of Warcraft uses a repair system to act as a dynamic money sink. For a starting character, repair costs are very small. As the character progresses, repair costs get more expensive to counter the increased money gain. Another example of a dynamic money sink is the fee charged to use the auction house. A percentage of the sale price on all auction house purchases is taxed by the game, removing that money from the system. Because it is a percentage, in times of inflation more money will be removed from the system, helping to curb the inflation.

Eve Online has a player-driven economy with some NPC merchants who curb inflation by fixing the prices of many items. Basic blueprints and skill books bought from NPCs are inexpensive, even for new players; however advanced blueprints and skill books, such as those required for capital ship production and flight are thousands of times more expensive. These are generally only of interest to veteran players, reflecting the desire to remove money in proportion to each player's wealth.

The second half of the article is lacking any citation, but a lot of it makes sense.

As far as the examples you mentioned, most of them sound like what's already planned or has started to see some form of implementation in game.

Rep Grinding is analogous to Guild Marks and GC Marks. Possible trend of making other 'factions' offer rewards for collecting marks. (Friendly Beastmen tribes like the Goblins, or neutral nations like Ishgard seem likely)

Item Enhancement will be our Materia system. (Which coincidentally, also serves to remove equipment from the game)

Transport is of course, airships, chocobos...

Not sure what you mean by 'Item Collection' and 'Item Turn-ins' though. Can you elaborate on this?

Edit:
Also an interesting quote from the Virtual Economy article:

For a persistent world to maintain a stable economy, a balance must be struck between currency sources and sinks. Generally, games possess numerous sources of new currency for players to earn. However, some possess no effective "sinks", or methods of removing currency from circulation. If other factors remain constant, greater currency supply weakens the buying power of a given amount; a process known as inflation. In practice, this results in constantly rising prices for traded commodities. With the proper balance of growth in player base, currency sources, and sinks, a virtual economy could remain stable indefinitely.

As in the real world, actions by players can destabilize the economy. Gold farming creates currency within the game more rapidly than usual, exacerbating inflation. In extreme cases, a cracker may be able to exploit the system and create a large amount of money. This could result in hyperinflation.

In real world entire institutions are devoted to maintaining desired level of inflation. This difficult task is a serious issue for serious MMORPG's, that often have to cope with mudflation.