I haven’t checked the in game market for them but aren’t higher level monster gems rather valuable? If you could attach them on some low level equip no one bothers to search from market, these pliers item might be used for stealthily transferring them inside those equips.
This could make new kinds of silver transfer methods possible? At least RMT based on the gems themselves if the gems have no selling to npc value. You could always re-attach the gem on some new equip to transfer it to someone else, who then takes it off for his equip, making the gems being tradeable infinitely, with little risk involved of course.
