Basic Price Guide
Due to the fact that the market changes so much, it is best to research before buying or selling anything of much value. Do that through use of the Trade channel in game and also researching prices in such places as Guild Wars Guru.
Materials - the NPC material crafter and rare material crafters allow you to buy and sell to them at any time. These items are often able to be bought for much less from a playing character, so always try that first. Generally, you can get stacks (250) of most regular materials for about 1 - 2platinum. The rare materials all differ greatly, with the Globs of Ectoplasm being the highest. Generally though, these go for around 6-7 platinum each.
Consumables – generally a set of Eye of the North consumables costs 7-8k and includes the Armor of Salvation, Grail of Might, and Essence of Celerity. Title related consumables generally go for: Party items – 150-200 gold per point, Sweets – 130-150 gold per point, Alcohol – 90-100 gold per point.
Tomes – these go up and down as skills are enhanced or nerfed. However, generally speaking, regular tomes go for 400-800 gold each. Elite tomes also change very often. Generally, they sell for around 6 platinum. The ones selling for more (up to 10 platinum) right now are for: Ritualist, Monk, and Necromancer.
Weapon Mods and Inscriptions – these change often too. Generally though, most mods are sellable because people need them and don’t always hang onto their own. Max mods can sell anywhere from 1k – 15k. Some rare ones might even bring as much as 170k, so research before you sell!
Minipets and Everlasting Tonics – minipets are given as birthday presents to each character every year. It takes a long time to get certain minipets, and some are only available through contests or certain codes, and the rarity of these minipets make the prices go up. Minipets price range varies from 100 gold to over 1000 ectoplasm! For an up to the date guide on these, check Guru’s minipet section. Note that non-dedicated means that they are “clean" and not already dedicated to a character’s Hall of Monuments, so you can then add them to yours. If it is dedicated, then you can still have it follow you around, you just can’t dedicate it to your HoM.