Just a couple of problems with the Market Boards.

[Kazamoto]

As Xystic puts it, your definition of equilibrium seems to be a static price, but that is not the case.

I only defined it as such, in my example that assumed demand was unchanged and supply was only changed to a very minor extent.

However momentum is a short-run effect. Even at lower price, demand actually increase because the item is now affordable to more people.

In the real world this is true, there will always be more buyers and investors willing to buy items given the right price. In the game (and without buy order options) unless someone is regularly checking the prices, demand would not necessarily increase just because the price went down. This early on, there is only so many crafters, or people leveling certain classes that have need at any one point.

Just because the price of 'Woolen underpants of itchiness' has decreased, it does not mean that there are more people who are leveling underpants gnome of the correct level to use the item.

In a higher turn over market, there may be market speculators that buy up a stock at low price assuming the value will go up, I'm doing this with some items in preparation for 2.1

Another example at the far edge of reality.
If someone could catch syphilis for $100 yesterday, and $25 today, is there suddenly going to be a rush on getting syphilis? Or is syphilis demand going to stay low no matter the cost?

If it stays down at that price, that means people are still able to make a profit selling at 50% of the old price, and you were selling it too high to begin with.

This makes the assumption that when undercutting, people still pay attention to if they are profiting or not.

I'm indifferent towards tax at listing or tax at selling. You think that tax at listing will eliminate undercutting...but in reality, it only serves to hide undercutting. Supply and demand drives the price, tax...only a little.

What will happen is that players will be more cautious about their pricing, and will try to sell at a price that has the highest probability of clearing the market, which means lower price...so Zigkid3 is right that it will drive the price towards equilibrium quicker.

It would not eliminate undercutting, but it would reduce knee-jerk price adjustments. As I have said, even if supply and demand are driving the price, it only takes one person who does not care about their own profits, to cause a downward spiral and destabilize an item.

Some would argue that more cautious pricing is a good thing, as it prevents sellers from using exorbitant mark ups.

Zigkid3 has repeatedly said that a presale listing fee would slow the drive to equilibrium.

However, this also introduce what we call sticky price due to the cost associated with changing price (you were right about the real world relationship of this). What sticky price does is that the price level is less responsive towards the change in supply/demand...meaning that if most people are posting at 100g now, but the equilibrium had shifted up/down, then the buyer/seller will lose out/gain...until the price level catches up to the new equilibrium.

I think the market should be slightly less responsive, this way undercutters can have their stock bought out without crashing an items value, and sellers would have a more difficult time trying to spike the price of an item.

So, it your motive of wanting a tax at listing is so that price level will hit equilibrium fast, kudos to you. If you want a tax at listing because you think it will eliminate undercutting and makes you able to sell your item for higher profit...then you're right for the wrong reason.

The tax, or fee to use the market board service pre-sale would do both, but it would not eliminate undercutting. Nothing will stop under-cutters, but it will reduce their impact on the market.

If I have to point of a problem with the market board, I would say it's the player's lack of understanding on how economics work.

There is a difference between a lack of understanding and a willful ignorance.
When people don't care, issues are caused. Internets are serious business.
Altana, I miss the EvE markets sometimes. The Jita spam...