Tag Match

Template:Verify Most NPC vendors buy items back at 80% of the item "value". A few select vendors will pay a full 100% of the item value. Portalarium calls this a "tag match". Any particular NPC may offer a tag match price for more than one item category.

To identify such vendors, simply see what a vendor will pay you for a given item, then see what a completely unrelated vendor will pay. It will help to have a single un-stacked item in your inventory, or you can control-drag a single item to the exchange pane. Items with a value of less than 5g will always pay full value due to rounding.

Note that what any NPC will pay for an item with a durability stat is affected by the durability. This is mostly important for weapons and armor. A weapon at less than 100% of brand new durability will sell for a lower price, but is still subject to a tag match mark-up.

Alchemist

These vendors will offer 5g each for Gold Ores and Silver Ores, 200g for uncut gems, 40g for Mystic Graff Gems and some NPC's offer full value for potions.
Aerie: Eretria Moonglow (159, 30, -62)
Ardoris: Johann Morton (27, 53, -122)
Ardoris: Saera Nightbloom (32, 53, -148)
Desolis: Alexa Herbstile (-341, 118, -121)
Desolis: Magus White (-301, 118, -131)
Etceter: Willard Warren (77, 2, 23, 7, 39,5)
Kingsport: Alicia the Alchemist (90, 26, -3)
Kingsport: Julia the Alchemist (77, 25, 0)
Owl's Head: William (95, 72, 45) Full value for Potions.
Port Graff: Alchemist (90, 25, -49)
Resolute: Parthalas (-11, 78, -209)
Solania: Cerrith (80, 18, -60)
Solania: Terrence (80, 18, -57)
Spite: Amy Zand (133, 45, -44)
Yew: Alchemist (Yew) (-1, 34, 1)

Blacksmith

These vendors will offer 5g each for Iron Ores and Copper Ores, and 50g each for Nickel, Tin, and Tungsten ores.
Aerie: Henry Steel (110, 31, 38)
Aerie: Ives Sinclair (123, 31, -51)
Crooked Shank: Soren (114, 69, -3)
Etceter: Aaron Denbo (100, 24, 34)
Etceter: Ezb Krohon (66, 24, -30)
Owl's Head: Blacksmith (98, 87, 238)
Resolute: Tobias Barnett (-30, 78, -235)
Solania: Tania (89, 18, 4)
Soltown: Annika (-43, 27, 6)
Spite: Calarth d'Havenstead (8, 38, -165)
Spite: Combat Merchant (0, 38, -161)
Spite: Combat Merchant (103, 45, -49)
Spite: Randy (113, 45, -52)

Tailor

These vendors will offer 40g each for Beetle Carapaces, and 200g each for Black Cutworms.
Ardoris: Christoph Schneider (80, 53, -151)
Owl's Head: Fred (75, 72, 85)
Soltown: Edwin (-42, 27, 13)

Weapons and Armor

These vendors will offer a higher price for weapons, or armor (or both), up to full value for like-new items.
Aerie: Oakie Lawrence (-40, 35, 219)
Ardoris: Zangoff (57, 53, -80) Full value for crafted weapons and armor. Highest price for dropped weapons and armor.
Brittany Alleys: Torulopsis Pengembara (27, 45, 46)
Brittany Alleys: Combat Merchant (96, 32, 395)
Brittany Estates: Combat Merchant (124, 74, 481)
Central Brittany: Combat Merchant (360, 32, 395)
Etceter: Aaron Denbo (100, 24, 34)
Owl's Head: Theo (93, 87, 226) Full value for crafted weapons and armor. Highest price for dropped weapons and armor.
Resolute: Whitten (-27, 78, -254)
Solania: Tania (89, 18, 6)
Soltown: Annika (-43, 27, 6)
Soltown: Martin (-25, 27, 0))
Spite: Calarth d'Havenstead (8, 38, -165)
Spite: Combat Merchant (0, 38, -161)
Spite: Combat Merchant (103, 45, -49)

Obsidian Chips

These vendors will offer 10g each for Obsidian Chips.
Owl's Head: Tanderly (61, 86, 217)

Crafted Animal Headdresses

These vendors will offer 50g each for Bear Headdresses and Wolf Headdresses and 25g for Boar Headdresses and Stag Headdresses.
Owl's Head: Theo (93, 87, 226)
Soltown: Martin (-25, 27, 0))

Repair Kits

These vendors will offer 10g each for Repair Kits of all types.
Crooked Shank: Soren (114, 69, -3)
Owl's Head: Blacksmith (98, 87, 238)