Items for auction are more expensive than they might otherwise be because there is a fee charged for each item; if the item takes many days on average to sell, then the seller must increase the price to compensate. On the other hand, due to the curious economy of MMORPGs, much of the goods at the Auction House were obtained for no more than time, and their value has nothing much to do with overhead costs; they are priced according to the Law of Greed and Desperation (aka the "Law" of supply and demand)
The Auction House is a very good place for new players to absorb as much as they can about what is valuable in PWI. The list of All that is currently for sale will seem a daunting prospect, and it may take more than an hour to search completely, but it gives a much better idea of the consistency of the PWI economy, faster, than does searching for individual items.
In short, the economy can, in these latter days of the game's development, be separated into two categories, and perhaps a third that incorporates a little of each. Utility, Fashion, and arguably The Edge. The Edge is the last little thing that a player needs to make their character as strong as possible; it offers little reward in comparison to Utilities like Armor and Weapons, Gems and Refining, but if they do not have it, they will be at a disadvantage. New players should avoid Fashion and The Edge; both demand a premium price and, for the most part, get it.
The first thing to understand about the Auction is that the Starting Bid is not a parameter you want to set low. It is no more than a romantic notion that there will be a frenzied flurry of buyers waving their arms to be seen, all hellbent on purchasing your item, raising the price dramatically. This may even happen outside of Hollywood, but it most certainly does not happen in PWI; it is much easier to simply big the next higher increment, which is only a small percentage of the current price. People will pay attention to the Starting Bid all right, and they will bid against each other to buy, but only if that Starting Bid is set too low. Such "bidding wars" are far more likely to end because one of the players had to go to sleep, rather than being outbid by a price too high for them to pay. Whereupon you will be selling for less than the item is worth. The Starting Bid is, instead, a fallback price that you will accept if the main price is too high for the market. Best to keep the two close together, and sell the item again at the same price; part of auctioning is waiting for your customer. You should not be selling items that go for mere thousands, but for hundreds of thousands, where the 500 or a thousand auction fee is a trifle, and you can afford to put it back up for auction repeatedly.
A few items can be sold by Consignment Shops (catshops) but can not be entered into an auction. For example, the Martial Arts scrolls that a character can receive from the Perfect Questmaster. These are very valuable (before they get turned into Silkworms at the Martial Arts Master, as they can then not be traded); they can be transformed into the direct equivalent of Training Esoterica, which sell for around 100,000 coin each. But they cannot be traded in the Auction House
The fee is based on PW's estimate of what the item is worth, not on the asking price.
Items that do not sell at Auction are returned to the player, along with half the fee. As the items are returned to their Mailbox, this an additional way to store items for a small fee.