I've seen this to be the case ever since the Giant Excavator buff (from FP) and the instancing of it on EU Scourge. Which is very neat! But the amount of stone that has been produced with it through some players has been insane. It's so easy to buy tons & tons of Diesel Fuel with Low Grade Fuel at Outpost that you can just dump the GE full and wait for it all to come in.
Another suggestion with that could be to potentially limit (or remove in extreme situations) the ability to buy Diesel Fuel with Low Grade at Outpost . It would reduce alot of the stone generated into the server & encourage people more to pick up the old pickaxe and actually go mining & work for their mula XD