We Need More Writers!
I don't think people realize just how patient you have to be on the trading post. The entire concept of waiting a day or two after you win all your buy orders seems so foreign that most consider it to be an insane way to play. When you farm monsters, you then sell the resulting loot a moment later. But farming the trading post can't work the same way. Because of the fees and everyone else doing the same thing, it doesn't work or if it does, you make very little profit for the time invested.
This is why flipping armor works so well, even if you are a novice who places hundreds of 1-3 buy orders at a time. You are FORCED to wait because the buy orders never get fulfilled quickly, which means that you end up coming back to the game hours or days later. Patience is forced by necessity.
But with faster moving markets, you can get thousands of buy orders fulfilled in a minute. This leads to the misconception that NOW is the same time to sell as it is to buy. No, no, no! Hold on to those items, wait a day or two just like with the armor! Why? Competition. Your competition is not patient enough, which means that you will have a much easier time selling when they all are finished updercutting each other and the prices go up naturally. You'll make more gold due to the price rising and you'll suffer less losses from cancellation fees.
Some items go up and down fast enough that you can trade within an hour or two of winning your buy orders. But you do not want to trade the same moment you acquire the items. Take your time, watch the market, and strike after everyone else finishes fighting for the first sale.