From Bulbapedia, the community-driven Pokémon encyclopedia.

A valuable item is an item which generally serves no practical purpose other than to be sold, usually for a high price.

In Generation II and IV, it is possible to buy some of these items for a discount (but only one of each per day) on Mondays in the morning in the Goldenrod Tunnel.

In Pokémon Black, some of these items are sold in Black City, albeit for prices much higher than they can be sold for. Often, these items later become exchangeable items. In Generation V, mulches and flutes became valuable items due to losing their function. While most of these items can be sold at Poké Marts, those introduced in Generation V can only be sold to certain item maniacs. Besides Big Nuggets, Pearl Strings, and Comet Shards, the player can also sell normal Nuggets, Pearls, Big Pearls, Stardust, and Star Pieces to the maniac inside the Icirrus City Pokémon Center, for double the price presented below.

Valuable items that can be sold in Poké Marts

Mulches

Main article: Mulch

Flutes

Main article: Flute

Valuable items that can only be sold to item maniacs

The following items have only been made available in Generation V for the express purpose of being sold to the Billionare maniac in Undella Town. Like many valuable items introduced in Generation V, they cannot be sold normally in Poké Marts.

Artwork

Underground

This is artwork of the items as seen in the Sinnoh Underground.

Global Link

This is artwork of the items as seen on the Pokémon Global Link.

In the anime

In Reunion Battles In Nimbasa!, a Pretty Wing was included in the full set of wings that was promised as a prize for winning the Club Battle tournament. The set was eventually won by Iris, who later sent it to the Village of Dragons.

In Defending the Homeland!, Clemont mentioned having used Big Mushrooms as a part of the new food he had just made for the group.

In Treasure Hunt, Akala Style!, Mallow found multiple Tiny and Big Mushrooms and Sophocles found a Star Piece during a Stoutland Search treasure hunt set up for Ash and his classmates by Olivia. In the dub, the Star Piece was incorrectly referred to as a Comet Shard.

A Nugget appeared in Why Not Give Me a Z-Ring Sometime?, where a man was seen polishing it, only to have it stolen by an item-snatching Gengar nicknamed "Greedy Rapooh".

In A Recipe for Success!, Mallow got some dried-up Big Mushrooms from Oranguru to be used at Aina's Kitchen.

A Pretty Wing

Big Mushrooms

Tiny Mushrooms

A Star Piece

A Nugget

In the manga

A Star Piece in Magical Pokémon Journey

In the Magical Pokémon Journey manga

In Hazel VS Almond!, Almond won a Star Piece in a contest held by Grandpa, giving it to Hazel.

In the Pokémon Adventures manga

In Ursaring Major, Team Rocket had cut off the tails of a herd of Slowpoke by the Slowpoke Well near Azalea Town, planning to sell them for profit. However, they were stopped by Silver and his Ursaring before they could do so.

A Big Pearl appeared in Crossing Crobat, where it was retrieved by Janine as a part of a test to check the security of the Goldenrod Museum.

A Big Mushroom appeared in A Week to Go and Old Wounds, where Shoko gave it to one of her Patrat to hold while demonstrating her Marvelous Bridge Patrat Show to Black.

In the Sun, Moon, Ultra Sun & Ultra Moon chapter, a pair of Team Skull Grunts sold grilled Slowpoke Tails at the Iki Town festival, with one of said Tails appearing in The Party Crasher and Guzma the Destroyer.

Slowpoke Tails

A Big Pearl

A Big Mushroom

Trivia

The Slowpoke Tail is actually a useless item with no function past its monetary value. Although it is said that a Slowpoke will use its tail for fishing, a Slowpoke Tail has no effect on fishing at all, nor does it have any effect on Shellder despite the fact that contact with a Slowpoke's tail usually induces a spiral change.

The first time that humans eating Pokémon is mentioned explicitly in the games is when a Team Rocket member mentions the SlowpokeTail's value as a delicacy. In Pokémon X and Y, Slowpoke Tail is one of the dishes served by Restaurant Le Yeah in Lumiose City.

The Japanese name for nugget, きんのたま kin no tama , literally means "golden ball", which is also a colloquial term for testicles. The man offering his "golden ball" is a frequent joke amongst Japanese fans. As this pun would be lost in translation, as well as the fact that it would not go over well with parent groups, it was translated as "nugget of wisdom".

, literally means "golden ball", which is also a colloquial term for testicles. The man offering his "golden ball" is a frequent joke amongst Japanese fans. As this pun would be lost in translation, as well as the fact that it would not go over well with parent groups, it was translated as "nugget of wisdom". The Rare Bone and Thick Club share the same Bag sprite.

The Relic Gold and the Comet Shard are tied for the highest-selling items in the core series, selling for 30,000 each.



