High-Quality Items
These items are the finest available -- they are ornately decorated with filigree and inlaid gems, and are better balanced and more comfortable to use than similar items of their type, and are slightly sturdier. High-Quality Items cost more: 100 gp for a simple weapon or light armor or a shield, 150 gp for a military or superior weapon, heavy armor, or implement, and 50 gp for other sorts of items (such as adventuring gear). Fortunately, they also count as "art objects" and thus can be sold at full price.
Special Components
You may find ritual components that are worth more when used in a certain fashion. For example, if you have 200 gp worth of elemental fire, it functions as 100 gp worth of alchemical reagents, OR as 400 gp worth of reagents when used in a fire-oriented ritual (such as granting a weapon a flaming enchantment).
Rituals
Disenchant Magic Item: This ritual disenchants the item without destroying it. It becomes a non-magical High-Quality Item which can then be sold or re-enchanted. Disenchanting produces residuum in value equal to half the market price of the item (not one-fifth market price).
Enchant Magic Item: This ritual can only be cast on a High-Quality Item. In addition, you can use it to improve the enchantment of an existing magic item. The material component cost of doing so is the difference between the market price of the new item and the market price of the original item. See "Enchanting Items," Adventurer's Vault, p.198.
Transfer Enchantment: This ritual (from Adventurer's Vault) is allowed, but might not always work. Certain enchantments are linked to intrinsic physical properties of the item and may not be transferable (e.g., a cold iron weapon).