There are two sides to trade in Guild Wars: the game side and the player side. The game side is simple: NPC merchants sell their wares at prices that fluctuate a bit due to supply and demand. If the economy goes completely crazy for one item (think Spiritwood Planks when the Black Moa Chick was introduced), prices will jump, but the merchants will simply "run out" of that item before the cost has a chance to get really out of control. If demand is very low, prices for both buying and selling will drop to an established minimum and stay there until the economy dictates otherwise. The system is set up so everything stays at a reasonable rate.
The player side is much, much more volatile. It's an open market, where the prices are dictated entirely by the community according to several factors. They're pretty standard value factors in any economy: difficulty in obtaining the item, how rare it is, or how new to the market or fashionable it is. These all play a part in determining worth. Items fall in and out of favor, with prices spiking as an item comes into the spotlight for whatever reason, then declining slowly over time. Weapons come and go -- Elemental Swords, Icy Dragon Swords, Celestial Compasses all enjoyed their day in the sun until new weapons such as the Bone Dragon Staff, Silverwing Recurve Bow, and Dryad Bow took their places over time.
Miniatures have the same rise and fall, albeit at a much, much slower rate. The peak prices come as character birthday presents begin rolling in, with the golds and greens taking as much as a year to drop to something the general populace can easily afford. Last May, for example, the going rate for a miniature Jora was well over 100k. Now the undedicated miniature can be had for around 30k everywhere you look.
The consequence of a nearly five-year-old game economy is that there is very little in-between left in the game at first glance. Nearly anything you need can be had for well under 10k, which is a negligible amount for most players. Elite tomes are at the top of the list, with prices on this profession or that taking a jump as the current flavor of the month skill comes to the forefront. Even max armor can be had for 1k plus some inexpensive materials. At the other end of the scale, you'll find prices in the stratosphere. Weapons and minipets selling for such exorbitant prices that the cost is measured in ecto rather than gold, because 100k won't even begin to cover it. On both the player and game sides, things like Chaos Gloves and miniature Zheds are priced so far on the opposite end of the scale from a +30 bow mod they're not even in the same time zone.
A healthy, ideal game economy is one that's nicely balanced across the board, with a decent amount of items being traded all up and down the pricing scale. Now Guild Wars certainly has mid-range items on both sides. Elite armor can be purchased for 10-15k per piece plus some more high-end materials. A quick trip to Kamadan or a trading forum will show items here and there such as a miniature Celestial Tiger for 40k. But the vast majority of items are at either end of the scale.
So what's to be done about it? Well, nothing really. This is just the way it is in a game that's been around long enough that the majority of the community has had time to obtain nearly everything they need and want. Most of the players have almost completely discretionary income these days, so to speak -- trying to scrape together enough platinum for max armor, runes, or a decent weapon is a thing of the past for those people. Introducing new items to the game doesn't solve anything, it just adds another thing to the heavy end of the pricing scale. An economy full of wealthy people is pretty nice overall, but keep in mind it has a counterpart: the people at either end of the scale. They're a minority, but there are players that are new to the game. To newer players, 20-30k is a pretty large amount of cash and the game can be viewed as a bit overwhelming. "Wow, that little fairy is neat." "What? Oh, that's a minipet." "Cool, how much was it?" "About 55 ecto." "What's ecto?"
Help them out. If you put out the call in guild chat for a full Fissure of Woe clear, that's going to sound pretty scary to someone new. (And telling them it's okay because you have Discordway won't help. They don't know what you're talking about.) Share the wealth a bit by helping new players out. Please note: I'm a fan of teaching a man to fish. If you're begging in Kamadan, I'm going to explain to you that you need to run outside that little swirly door over there and start swinging. So I'm certainly not advocating that you descend on AD1 and start flinging cash about. But I am suggesting that you see who's new and confused in your guild or alliance, or who never seems to have the cash to buy what they need, and help them out. Teach them what to do to play the game well, because the first step to picking up cash is being alive to get your loot. Teach them about collector weapons and armor. Play with them a bit -- not to do it for them, but to help them learn. It's a small step toward a more evenly balanced economy when a new player who previously viewed 1k as a lot of money is tearing through mobs in hard mode and filling their inventory.
Then you can teach them about merchant summoning stones.