Given the majority of players use Relics and the high demand there is for pluton as well as the random nature of what type of REM item you can recieve, creating an npc similar to Shemo that would convert 2 or 3 of a Riftborn Boulder / Beitetsu / Pluton into 1 of an REM item you desire would be practical.

At present on the Sylph server prices are:
200~300K each for Pluton (60~90M for 300/300)
20k each for Riftborn Boulders (6M for 300/300)
10k each for Beitetsu (3M for 300/300)

At the very start you could trade amongst players, but then the value system fell apart in a matter of 2 to 3 weeks based on what the majority of players actually own. Please consider the addition of this npc to make it more feasible to ilvl119 relics.