Hi,
I can think of two reasons why you pay a deposit fee for selling stuff in the auction house:
- to reduce the money in circulation
- to balance the price
The deposit fee depends on the type of item, its normal merchant value, the stack size and the duration it is placed for in the auction house. Needless to say, the normal merchant value has little correlation with the value for other players. The normal merchant values are not even consistent. For example, one piece of Linen Cloth has a sell value of 13 copper, while one piece of Shal’dorei Cloth, which plays in an entirely different stage of the game, only amounts to 1 copper. Both have a deposit value of 2 silver @24 hours due to a minimum limit but e.g. Embersilk Cloth, which occures between both, deposits for 5 silver @24 hours. It does not make sense.
Despite people always saying ‘supply and demand’, the prices are frequently not stable in the auction house. Moreover, there are a lot of items continuously listed for exorbitant amounts. This type of extortion is basically not penalized because the deposit is not bound to the listed price and low comparatively. While exorbitant sales are not likely to succeed (unless accidentally), it distorts the appearance and items that are not listed for exorbitant but still very high prices will eventually be bought after enough time passed because at some point, there will be no competitor and either urgency or a customer who possesses too much money, who does not care. Unlike in the real world, there is no decay attached that would force the provider to make a move. Also, using an exorbitant price tag, the auction house can be effectively abused as additional storage for sellable items for low costs.
Conversely, the minimum limit penalizes non-profit items. Items cannot be offered for free or an obolus unless you want to go in the red. There are items too valuable for deletion or selling to normal merchants, which would be nice to donate to the common good or just for the joy of trading, yet this practice is stalled.