Commentary:
Not a new idea, it simply promotes a more active and fluid economy, giving everyone the opportunity to trade more freely. Stalls are a common method of selling goods on old MMO's, some games that still use them are Ultima, Uncharted Waters 2, Voyage of the Century, and Silkroad. Some of these have expanded stall features, such as global tool for searching stalls (Silkroad and Voyage of Century) or added a limited auction house in addition to (Uncharted Waters), I do not know of any new MMOs with a stall system. The issue is with dealing with them is you almost never get a fair market value on anything you buy, hard to find what your looking for, and hard to find the numbers you want. JC posted iron bars average selling price at almost 31, that price would be closer to fair market value except many would sell them for less with manual trading to avoid the stall taxes of course.
Auction houses are virtual trading through a broker npc. The most advanced auction house I have seen had these features.
Features
1. Ability to sort your search by item type or manual searching.
2. Ability to sort by price and enter the range. (Finished goods such as clothing with attached artifacts would be useful, whereas same type large range of cost)
3. Posting fee's and time, Posting fees typically fairly low 5-10% of total price your posting it for, and the post lasts for 7 days, being able to increase time for additional fee.
4. Sales Tax, both Seller and buyer pays a 5-10% sales tax each.
5. Posted items could be a group of items. Stalls have the option to sell by groups.
6. Ability to place buy orders (Could include restrictions aka purity requirement).
7. Ability to actually auction items including a buy out price.
Example:
So for a typical transaction at the lowest possible, you would pay 5% posting fee, then charged 5% on sale, if you don't sell the item within 7 days you get the item back however lose the 5% posting fee, as a buyer you are also charged 5% sales tax when purchasing. So you post something for 100s, you pay 5s upfront and charged 5s for total of 90s, The buyer pays 5s as well as the 100s. total tax collected on 100s would be 15s or 15% overall.
Posting fees are made to discourage unreasonable pricing, if you purposely overcharge you will lose your money posting it. Sales tax is simply convenience, the higher it is, however causes less trading, to the point where you never use it cause it cost you more than its worth. High Posting fees can have the same effect, posting fees are usually equal to or higher than sales tax to prevent bad posts.
Effects:
Auction House primary focus is to encourage heavy trading on a massive scale. They also require no dev involvement, such as placing stalls. The main difference is stalls are easy to develop and implement and a auction house is major feature that by itself drastically changes the nature of the game. Auction house would take time develop and prevent development of other features.
To keep overpricing, limited selection, unrealistic forum trading, high trading cost, to avoid small trades, and give playing Salem a focus that is not trading, then we need to keep the stalls we have. The economy is not currently a Salem feature. We have stalls with a select few traders using them, costing them a great deal to trade while selling inflated pricing on items. Many seem to be pretty happy with this, I always found the hard rejection of auction houses confusing, but ok. I don't know why making a good economy on Salem would be a bad thing.
I do understand making a auction house being too difficult for the devs to develop for Salem or simply don't want to develop such a system at the cost of developing other new systems and features. I still wouldn't ever take it off the table on ways to improve the game.