Coin does not leave the Istarian economy very often. The two main ways that it occurs is when people buy plots, and the charge for being teleported somewhere. However, buying a plot is usually a one-time affair, and the cost of using portals is negligible for any established player. The end result is that coins have been collecting in the game world and they don't have any way of escaping.
This is a bad thing because it means that coins aren't useful. You can't do anything with them and it makes trading between players very difficult. Why would I accept something that's useless (if one already has a plot) in exchange for valuable tech resources, for example? The only time that trading is likely to occur is when two players happen to each have an item that the other wants at the right time (because most players do not have a lot of storage space lying around), and given the relatively low shard populations, this just doesn't happen very often.
My suggestion is to create a new kind of pawnbroker. This pawnbroker would have limitless stocks of every kind of resource in the game (and perhaps expert formulas too). The prices that the pawnbroker would go up as the players bought more resources from him, and the prices would fall again as players sold their resources to him.
For example :
Let's say the pawnbroker is selling unspun flax at a price of 10c each. I'm in a hurry and I want a lot of flax fast, so I buy 1000 flax. Suddenly, the price for flax is now 30c each. A lvl 40 gatherer comes a long with a cargo disc full of 500 flax and sells his unspun flax instead of processing it. The pawnbroker's selling price for flax now falls down to 15c each.
The numbers in the previous example are made up to demonstrate the principle. Because the prices would vary, the cost for buying from the pawnbroker would quickly mirror whatever people thought was a reasonable price for the resources, given the time it takes to harvest them. From a game mechanics standpoint, one could create resources using coins, giving them a purpose (much like you could use Nadia to create tech resources by buying them from her).
Players would still be ultimately responsible for the game economy, because if no one sells their wares to the new pawnbroker, the prices would quickly become exhaustively expensive (who would pay 10s per spool of flax, for example?) This would also mean that we wouldn't have to worry about the players who purportedly have over 1 000 gold breaking the system.
Also, this would allow players to use their crafting levels to subsidise their adventure levels, and vice versa. A player that's good at adventuring could gather a large number of vexator fringes, sell them and then buy iron ore to level his blacksmith school. The crafters on the shard, conversely, could sell iron and buy the fringes.
Finally, I would recommend that for "bulk items" (silk, essence orbs, bars, ore, etc.) that the price should increase by 10% for every 1 000 bought or sold. For rarer items, the prices should increase or decrease for every 10 bought or sold. The pawnbroker should charge 15% more for what they sell, compared to the price they buy things for, as this will help to slowly move gold out of the game world and will also discourage market manipulation. The 15% fee will also encourage players to trade directly with each other, ironically enough, but I consider that an added (if unintended) bonus.