Such interesting food for thought. You are deceiving people for your own gains but then you're not breaking any rules (i guess since i don't know much about runescape), and it would really matter if it was an NPC who did that to them.
Is that wrong? Is it part of the game? Obviously there would be something wrong if you sold people your digital tokens and then took them away from players - you agreed to give them digital tokens and then took them away. But if an in-game character is making false representations as part of the game, that seems different.