Fantasy Costco

"Fantasy Costco, where all your dreams come true! GOT A DEAL FOR YOU!" Fantasy Costco is an independent retail store stocked with magical items and run by Garfield, the Deals Warlock. It is conveniently located on the Moonbase of the Bureau of Balance so Griffin can do all his character management at once.

Inventory
Note: Thanks much to Reddit user fishgutsd. No dogs! {| class="article-table" !Item !Sold to !Intro'd in Episode !Price (GP)
 * Extreme Teen Bible
 * Merle
 * Ep. 9
 * 350
 * Phantom Fist
 * Magnus
 * Ep. 9
 * 400
 * Ring of Pointing
 * Taako
 * Ep. 9
 * 200
 * Stone of Farspeech (3)
 * Magnus (for sharing)
 * Ep. 9
 * 100 ea.
 * Scuttle Buddy
 * Merle
 * Ep. 9
 * 500
 * Wand of Switcheroo
 * Taako
 * Ep. 9
 * 1300
 * Unlimited Pasta Pass
 * Taako
 * Ep. 9
 * 100
 * Alchemist Ring
 * Ep. 17
 * 500
 * Glasses of Lightning Comprehension
 * Merle (?)
 * Ep. 17
 * 600
 * Lens of Straight Creepin'
 * Magnus
 * Ep. 17
 * 700 (paid 700 for this, the Mystery Bag, and the Tankard of Potent Drink)
 * Mystery Bag (Steven)
 * Magnus
 * Ep. 17
 * 300 (paid 700 for this, the Tankard of Potent Drink, and the Lens of Straight Creeping)
 * Pocket Spa
 * Taako
 * Ep. 17
 * 900
 * Ring of Recall
 * Merle
 * Ep. 17
 * 1000
 * Tankard of Potent Drink
 * Magnus
 * Ep. 17
 * 300 (paid 700 for this, the Mystery Bag, and the Lens of Straight Creeping)
 * Anti-Gravity Sphere
 * Taako
 * Ep. 28
 * 500
 * The Champion's Belt
 * Magnus
 * Ep. 28
 * 800
 * Diadem of Fabulous Truthiness
 * N/A
 * Ep. 28
 * 900
 * Flaming Poisoning Raging Sword of Doom
 * spoilers
 * Ep. 28
 * 60,000
 * The Glutton's Fork
 * Magnus
 * Ep. 28
 * 750
 * The Immovable Rod
 * Taako
 * Ep. 28
 * 1100
 * Nitpicker
 * Merle
 * Ep. 28
 * 900
 * No-sodium Salt Shaker
 * Taako
 * Ep. 28
 * 400
 * Plastic Sheriff's Badge
 * Taako
 * Ep. 28
 * 500
 * Phone-a-Friend Scrybones
 * Merle
 * Ep. 28
 * 500
 * Rusted can of Cheerwine
 * Merle
 * Ep. 28
 * 400
 * Shield of Heroic Memories
 * Magnus
 * Ep. 28
 * 1200
 * All-or-nothing coin
 * N/A
 * Ep. 40
 * 700
 * Arcane Trickster's Glove
 * Taako
 * Ep. 40
 * 1500
 * Astro Shell
 * N/A
 * Ep. 40
 * 1200
 * Magnetic Charge
 * Magnus
 * Ep. 40
 * 900
 * Mathias, the Living Grimoire
 * Merle
 * Ep. 40
 * 1300
 * Mockingbird Gum
 * Taako
 * Ep. 40
 * 200
 * Mystery Powder
 * Ep. 40
 * 800
 * Strongmouse's Laughing Amulet
 * Merle
 * Ep. 40
 * 1200
 * Tarantula Bracelet
 * Magnus
 * Ep. 40
 * 800
 * Billow Branch
 * N/A
 * Ep. 50
 * 800
 * Grappling Hook
 * Magnus
 * Ep. 50
 * 600
 * Jar of Bees
 * N/A
 * Ep. 50
 * 200
 * Pocket Workshop
 * Magnus
 * Ep. 50
 * 1200
 * 1300
 * Mockingbird Gum
 * Taako
 * Ep. 40
 * 200
 * Mystery Powder
 * Ep. 40
 * 800
 * Strongmouse's Laughing Amulet
 * Merle
 * Ep. 40
 * 1200
 * Tarantula Bracelet
 * Magnus
 * Ep. 40
 * 800
 * Billow Branch
 * N/A
 * Ep. 50
 * 800
 * Grappling Hook
 * Magnus
 * Ep. 50
 * 600
 * Jar of Bees
 * N/A
 * Ep. 50
 * 200
 * Pocket Workshop
 * Magnus
 * Ep. 50
 * 1200
 * Jar of Bees
 * N/A
 * Ep. 50
 * 200
 * Pocket Workshop
 * Magnus
 * Ep. 50
 * 1200
 * 1200

Rickle Axager's Pocket Guide to Adventuring, Third Edition

 * Taako
 * Ep. 50
 * 1100
 * Ring of the Grammarian
 * Merle
 * Ep. 50
 * 800
 * The Slicer of T'pire Weir Isles
 * Taako
 * Ep. 50
 * 900
 * }
 * 900
 * }

Trivia

 * The Fantasy Costco theme song is a terrible, terrible earworm.
 * The clothing department of Fantasy Costco shoots out with shelves and racks of clothes like in The Matrix.
 * It is the only non-dome-shaped building on the moon.