A way to revive the Market from the "great depression?"
For example in Server 4, stone is almost impossible to sell as everyone sells for the minimum price, which is 0.01. Making a sell to NPC option for resources would mean no one would sell for minimum on the market anymore because they could just sell to NPC. This would mean they would try to get it sold at 0.02 which would enable people to get more money for their resources.
However, the price fo the sell to NPC must be reasonable and at a certain margin under the minimum price in the market, so to stop people from keeping on lowering their prices to meet lowering demands. This would also mean a greater demand for resources as resources would be going out of the system when sold to NPC (although this may be cancelled by the money coming in to the system.)
Another option would be to be able to sell for more precise prices. Say for example everyone in the market may be selling iron for 0.03, so being able to sell for 0.28 would mean not losing out on too much money if you want to get your resources sold straight away and still providing the buyers with cheaper resources.
I doubt these ideas are perfect, but they just might be able to help.