Each item really has different issues. The volatile phlog price was likely not because people were buying and flipping it, but because it was only reasonable to farm ~2,000 a day at most and each piece of gear with poor RNG gobbled up ~800 phlog. The demand shot up real quick because everyone knew they could save months of work. Now the demand is less than what it was, until more demo players reach 70.
Each time there is a long GK group, there is 1000s of phlog entering the game, and a year out from steam there is just not that much demand to reroll new sets of armor. If anyone knows they need phlog, for the love of god--just put up multiple small work orders. You WILL save money.

I believe most people reading this thread have a vendor stall. The vendor stall owning crowd is very different than those who don't open one. My recommendation is to look at the player work order board and see who is buying a lot of what, figure out the player vendor price and under cut their profits to either shift the price down, or screw the rich.

At times I feel in favor of barter-NPCs to dictate prices, but the hands off approach allowing the market and player population do it's thing is probably best. No one has the 'right' to get any skill/item. If the devs start putting their fingers into the economy now, they'll be doing it forever. However.. super-detailed-options, stall reviews ,etc on the player stalls would be an absolute game changer to the economy. It's really tricky to manage the economy with a transient population that hovers around 200 individuals. And let's face it, few people want to farm gems/stomachs, so the prices are high.

One player with 40 million could disrupt the entire economy for any given item. The hardest item to 'wreck' would be aquamarines due to the barter, but it could still happen. The only proper regulation against this would be a player stall revamp, giving the sellers a level of control that is not seen in any other MMO.