Right now, the item market works by selling the item for its wealth in GP. The reason some items are sold is because their "street" value is so high that they virtually cannot be bought using the GE.
For example, an item is worth 200m but has a "street" of 1b. You'll need to buy the item ingame with 1b--you'll receive the item plus 800m of junk. On Sythe, instead of having to spend 1b, you get it at the normal price plus some cash.
On Feb1, you'll be able to trade items without any wealth limit. That'll make things back to how they used to be in 07: you give the item for free ingame.