In the buy/sell menu, highlight any unwanted equipment. While holding the RT button, repeatedly press A. This works only on the items in the equipment menu (the shield icon), not the items in the Bag icon. This works in any shop, including the little fast travel buy/sell menu. This glitch may have been patched, and does not affect trophies. Note: The item you are 'cheating' with will be sold and gone when you release RT.
Grind in any level for maximum experience and get the Elfstone Of Congeniality, which offers a 10% discount on items. Equip ten of them, totaling 100% off. You can now get anything from the store for around 1 silver coin. You can also sell your most expensive item for 30,000, then buy it back for 1 silver coin, then sell it again for 30,000. The best place to do this is in the Ettenmoors. The specific time to start grinding for the Elfsones Of Congeniality is just after a save point, when the character Andriel says "I see sunlight ahead." To be exact, the first two Orcs are archers that you will kill. Take out everything and loot the bodies, but do not continue past the save point of the wooden gates. Go back to the closest Fast Travel, and go to Rivendell and repeat the process.
ACHIEVEMENT - HOW TO UNLOCK Where there's life, there's hope (10 points) - Revive a fallen ally. Foe-hammer (10 points) - Kill 200 enemies in a single playthrough. Sudden Fury (10 points) - Perform 3 critical hits within 10 seconds. Strength of Our Alliance (25 points) - Slay one enemy together with 2 other players. Seeker (20 points) - Discover 25 secrets in a single playthrough. Gem-studded (10 points) - Slot an elfstone into an item. Relentless (20 points) - While in Hero Mode, perform a streak of 50 hits. Now for wrath, now for ruin! (20 points) - Kill 4 enemies simultaneously. Troll's Bane (10 points) - Slay the wild snow trolls. Battle-master (20 points) - Unlock every active-cast ability in one character’s skill tree. War-hardened (10 points) - Achieve at least 1 rank in a tier 3 skill. Like a Thunderbolt (20 points) - Deal 3000 damage with a single ranged strike. Fell-handed (20 points) - Deal 1500 damage in a single melee strike. Living Shield (20 points) - Absorb 25,000 total damage during the course of 1 level. Many deeds, great and small (20 points) - Complete 15 quests in a single playthrough. War-machinist (20 points) - Kill 150 enemies with war machines in a single playthrough. Well-arrayed (25 points) - Equip a complete magical armor set. Keen-eyed Marksman (20 points) - Kill 50 enemies with headshots in a single playthrough. Swift-winged Warrior (20 points) - Summon Beleram 10 times in a single playthrough. Warrior Exemplar (25 points) - For one character unlock every skill that provides a modification to War Cry, Sanctuary or Evasion. Defender of the North (10 points) - Achieve level 10. Champion of the North (20 points) - Achieve level 20. Herb-master (10 points) - Create 15 potions in a single playthrough. Bane of Mordor (25 points) - Kill 600 enemies in a single playthrough. Dragon-hoard (20 points) - Amass 25,000 coins. Expert Treasure-hunter. (25 points) - Locate 5 gilded treasure chests in a single playthrough. Victorious in Battle (25 points) - Complete a playthrough on at least Normal difficulty. Against All Odds (80 points) - Complete a playthrough on Legendary difficulty. The Lidless Eye (25 points) - Complete the investigation of the Cult of the Lidless Eye. Hero of Legend (50 points) - Complete a playthrough on Heroic difficulty. Giant-slayer (20 points) - Slay Bargrisar the stone giant. Begone, lord of carrion! (20 points) - Defeat the Barrow Wight Lord. Trusted with the Secret (10 points) - Learn of the Ring of Power and the plan for its destruction. In the Dragon's Den (20 points) - Meet a dragon and survive. Friend of the Woodland Realm (10 points) - Free the elf from his captors in Mirkwood Marsh. Eagle Savior (20 points) - Defeat Agandaûr without the aid of Beleram. Friend to the Ring-bearer (10 points) - Speak with Frodo in Rivendell. Tharzog's Bane (20 points) - Defeat Agandaûr's lieutenant Tharzog. Mountain-breaker (25 points) - Help destroy the citadel within Mount Gundabad. Wulfrun's Bane (20 points) - Defeat the Sorceror Wulfrun. Tracker (10 points) - Discover what happened to the missing Rangers. Spider-slayer (25 points) - Slay Saenathra. Elf-friend (10 points) - Join forces with the sons of Elrond. Friend to the Eagles (20 points) - Help free the Great Eagle Beleram. Siege-breaker (35 points) - Help weather the siege of Nordinbad. Hero of the North (80 points) - Defeat Sauron's Lieutenant Agandaûr.