Selling gems and jewelry always fetches 80% of the object’s value unless the DM states otherwise.1) Characters do not lose any XP that has been awarded for these objects by selling them, since they are already in transportable form before being sold. Of course, if the object is sold prior to XP being awarded, such as to split the value among characters, then the XP is awarded based on the resultant coinage, which will be in total 20% less XP than a single character would have gotten had they kept the object.
This means there is a bit of strategy in choosing whether to sell or keep these items. On one hand, more XP and GP. On the other hand, it has to all go to a single character.
Extra effort or reaction rolls may be required to find a buyer for certain items.
When looted, spellbooks have a treasure value of 100/200 (xp/gp) per spell level contained therein.2)
See Magic Item for how to handle all these cases.
Whether or not to focus session time on magic item identification will be a decision that must be made by the DM when the DM is devising their campaign and recruiting players. A table that likes to spend hours experimenting with magic items to figure out their plusses or other effects will be enjoyable to some players and unenjoyable to others. There are also players who enjoy it but, given the choice, would prefer to use session time on adventure.
Some decision must be made, since there is the question of GP value of magic items, and how that GP value is affected by how much the PCs know about the item. Of course, the difficulty in selling these items once value is determined will also vary between campaigns. And whatever time is spent will increase dramatically as characters advance in levels and acquire larger amounts of magic per expedition.
If the DM wishes for the campaign to not spend extensive session time attempting to identify each item, the following rules extension is offered, which we have used at our table for a long time.
This section is a rules extensionEx and is not part of the official game rules.
If a magic item has been identified,3) the DM may inform the players how much XP it is worth if kept, and how much gold and XP if sold. If the item has not been 100% positively identified, the players must choose to keep or sell.
If they choose to keep an unidentified item, one character must take ownership of the item. XP is only awarded when the properties of the magic item have been positively identified. In the case of magic items with multiple properties, partial XP can be awarded. The DM must track the identification status of magic items.4)
If they choose to sell an unidentified item, the characters will receive the full GP value of the item, even if they didn't know any of its properties. However, they cannot change their mind about selling at this point! Once the DM tells the players the value, the item is completely gone. There is absolutely no renegotiating, stealing-back of the item, or otherwise re-obtaining the item. This is the risk players take when selling an unidentified item. In return, players aren't made to feel that they are missing out on potentially tens of thousands of gold if they don't spend 2 hours of session item tinkering with the item.5)
Note that full GP value will not be awarded if the seller did not even know the item was magic! For example, a magic gem “worth 100 gp” which is actually a magic gem of much more value would nevertheless sell for 80 gp (the 20% penalty for selling gems being applied), not the much larger sum. The seller must at least know that the item is magic in order to benefit from this rules extension granting full GP value.
If a PC wants to sell a magic item to another PC, no one receives “GP XP” for the sale. The PC that recovered the item receives “XP XP” for doing so, but never GP XP. GP XP is only earned when the item is sold on the open market, and all items sold on the open market leave the game.6)