How do you figure Market Value?
That's really the trick, isn't it? Some days I look at Table 8-40 on page 242 of the DMG and wish it wasn't there at all. At these times, I wish the rule was simply, “Match your new item as closely as you can with an existing item, then give it a similar price.” That's really the ultimate pricing rule. It can get you into trouble (as it did with me and boots of striding and springing), but generally it will give you fewer headaches than using the table. At the very least, we should have called the table "Estimating Magic Item Gold Piece Values" rather than "Calculating Magic Item Gold Piece Values."
But to answer the question we must discuss something about the question itself. The "you"in "How do you figure Market Value?" should ALWAYS be the DM. It should always be the last thing that's done in the process. Do not -- I repeat -- do not allow players to look at that table and see what they can make for X amount of gold. This isn't Champions or GURPS (see below).
So, you have an item either that you have created and want to put into your campaign, or that a player has proposed that he would like his character to make. If it's a straightforward item that's a potion, scroll, wand or staff, just use the formulas provided. Keep your eyes open, but feel confident that you can trust the system to handle those without a problem. But if it's not a straightforward item, be careful. Find a formula on Table 8-40 if you can, and see what the price gets you. Look on the charts at similarly priced items. Is this item of comparable use and power? If the answer is no, adjust the price until it is in range with items of approximately the same use and power.
Avoid the "disadvantage trap." That is to say, don't assume that, because an item has some sort of drawback, its price should go down. For example, say the elf Vexander makes a staff whose spells can be accessed only by elves. That might seem like a limitation. But really, it's not -- it doesn't affect Vexander in any way. In fact, if some non-elf steals it, the thief can't use it against him. It's actually a benefit. And even if an item really does have some true disadvantage, or has a cursed effect as described in the DMG (starting on page 231), don't discount the price too much; 10% is probably fine.
The most important thing to remember is, Table 8-40 doesn't determine prices. It suggests them. Don't say, "Wow, these shoes of continual improved invisibility sure are cheap." Do say, "Hmm, these formulas don't work when it comes to spells like improved invisibility." When someone asks me, "Can I really make an item that will cast cure light wounds at will, activated by a command word, for only 900 gp?"I now reply, "Only if your DM isn't paying attention."
The main problem is that spells aren't balanced in the same way as magic items. A single casting of improved invisibility, for example, might be equal to a single casting of locate creature. But an item that allows you to use improved invisibility at will is not equal to one that lets you use locate creature at will, because a character wants to cast improved invisibility numerous times a day, every day. Not so with locate creature. Spells are balanced because of their durations, and because casters only have access to a limited number of uses in a given day. Take those away, as with a constant effect in a magic ring, and the magical effects on the game need rebalancing.
The other problem is that sometimes there isn't a good spell equivalent for an item, or sometimes the closest spell equivalent is too low or too high a level for what the item does.
) defined as an "attack action".
