Can't find rules or FAQs about this.
We found a magic cursed weapon, and the GM also can't find anything about removing the curse from the weapon itself and making it a normal magic item.
Remove Curse can only remove the curse from a character wielding it (or just enable them to let go of the weapon and get rid of it), but specifically cannot remove the curse from a cursed shield, weapon, or suit of armor.
Break Enchantment doesn't work on items at all.
So, is there a way at all, as per the rules (short of Miracle/Wish)?
With the GM's permission, you could probably use the guidelines for Altering Magic Items from Ultimate Campaign to remove the item's curse. The GM can require talismanic components in addition to item crafting feats and the casting of remove curse during the "purifying" process.
There isn't really a way to undo the magic item's curse, but there are ways to remove the cursed effect once its been applied to a(n unknowing) user, and namely remove curse (and by extension break enchantment) do work. Example, the Girdle of Opposite Gender can only be removed by a remove curse or similar effect.
What can't be done is turning the item into an actual item, because the cursed item was an item that was failed to be made but so severely a cursed item was made instead of nothing at all, and thus wasting the resources. Essentially you can't gain money from nothing here.
That said it could be understandable if a GM let a player who spent 25k gp on the wish or miracle could make the cursed item into a normal wonderous item of lesser value. It's just not RAW anywhere that this is a specific thing one can do.
What kind of can get around maybe the above limitation is from the often cited as poorly thought-out "Ultimate Wilderness" book:
Raw Magic Item Materials: Anyone with an item creation feat can salvage the raw materials from magic items for the creation of new ones or repair of existing ones. You must have the item creation feat required for that item to salvage its raw materials. Each attempt requires destroying a magic item and 8 hours of work. If the item’s price is 500 gp or less, you can salvage its materials in only 2 hours. A successful Craft or Spellcraft check with a DC equal to 10 + the item’s caster level yields raw materials worth two-thirds the creation cost of the destroyed item (one-third the market price). If you fail the skill check by 4 or less, the item is destroyed but the materials can still be salvaged in a future attempt. If you fail the skill check by 5 or more, the item is destroyed and the materials are ruined. Salvaged raw materials can be used to create or repair any item made of similar materials or that shares any of the creation requirements as the original. Including the majority of the materials allows you to automatically meet any construction requirements of a new item that the salvaged item also required and reduces the construction or repair time by the proportion of the new item’s construction materials that are salvaged (with the usual minimum creation time). Spellbooks and formula books can be salvaged for magic inks and paper usable in formula books, scrolls, and spellbooks.
If your GM allowed this, which I'm personally not sure I'd recommend, you could in theory get back 2/3rds of the cost of the originally attempted cursed item's cost to try again by paying the remaining third again. That said, there are many issues, namely that you're likely wanting to salvage a cursed item you found randomly placed in an adventure, that you have no idea how much it costs if it even has an actual cost listed in the book.
Mh, as a group we're not fans of adding more and more systems or anyway make the game more complex than it already is...
Given the lack of simple and straightforward rules, I guess the GM will either keep the line of "cursed items are failed items, and that's just how it'll stay" or use some specific narrative solution, like a side quest to plunge the weapon in a sacred lake, using it to kill some particular monster to "redeem" it, or something like that.
Thanks for the directions.
This type of question often happens when a player/group finds a cursed item and wants a way to make it "useful" instead of just discarding it. Turning a berserking sword into a +2 furious greatsword, a biting battleaxe into a +2 mighty cleaving battleaxe, an unstable musket into a +1 reliable musket, an unwieldy glave into a +2 fortuitous glaive, etc.
The guidelines for Altering Magic Items in Ultimate Campaign is probably the closest we have in official rules. One way to handle it is to price it as double the cost of an upgrade from the basic "+X" weapon (both to remove the curse and then add the replacement weapon ability), require an appropriate talismanic component (something needing a quest to obtain), and the addition of remove curse to the crafting requirements (which cannot be replaced by adding +5 to the Spellcraft DC). The process can also only be performed after the curse is broken to allow the character to "discard/remove" the item.