As someone who used to buy every salvage on the market and re-list it for 10x the price to turn a profit, maybe it's better that it isn't possible.
Marketeering as you describe is simply accumulating wealth on individuals characters, taking it away from the masses.
While there were some positives to market manipulation (mainly providing a service of additional inventory), there was much more bad than good.
At the end of live I had around 150 billion influence, and I'd be lying if I said it I did it in an honest and good way. It sure was fun to accumulate that much, but it also had a cost for many more players.