How to get rid of quest items

From Destructoid:

Kingdoms of Amalur: Reckoning demo item unlocks for Mass Effect 3:

• Reckoner Knight Armor: This armor will maximize damage done in close-quarters combat while a beefed–up power cell feeds energy into weapon systems to increase projectile velocity.
• The Chakram Launcher: This weapon uses a fabricator to manufacture lightweight, explosive ammunition discs. This weapon is earned after completing the Reckoning demo and watching the trailer at the end.

Mass Effect 3 demo item unlocks for Kingdoms of Amalur: Reckoning:

• N7 Armor: Players can unlock special armor inspired by Commander Shepard’s iconic N7 battle armor including Helm, Cuirass, Gauntlets, Chausses and Greaves.
• Onmiblade Daggers: A holographic blade stemming from Commander Shepard’s Omni-Tool, the Omni-blade allows players to stab enemies in close combat. Once players install and play the Mass Effect 3 demo, they will unlock the daggers.

Kingdoms of Amalur: Reckoning demo item unlocks for Kingdoms of Amalur: Reckoning:

• Twist of Fate Card: This card boosts the player’s ice resistance and is immediately unlocked when he or she activates the Reckoning demo using his or her Origin account.
• Twinned Souls Chakram: A unique weapon that damages enemies while boosting player health and mana in Reckoning.
• The Infernal Helm: Unlocked after completing the Reckoning Tutorial Mode, this protective helmet increases players’ fire damage throughout Amalur.

Given that all the other quest items in the game, even the ones for quests you don't have yet, seem to be unsellable, I think it's safe to sell these off. Some Googling backs up the idea that they aren't used anywhere else:

Once you collect all five treasures scattered over Dalentarth (track the mission and see the locations), you complete the mission. Sell (or stash) all five if you like; they are worth roughly $800 per item (with no Mercantile skill increase).

On a related note, I tested and you can actually sell them off while the quest is still in progress. It's finding them that triggers progress and completion, not possessing them. So you can sell them off as you go to free up inventory space and the Treasures of Meropis quest will still complete. There is no need to wait until the end and sell them all at once.