There is a bug with the Rune of the Monk’s sell price. At Historian Symon the ingame description says the Major Rune of the Monk is worth 8s64c but if you try to sell it to Merchants it will say it’s worth 1s8c. I looted one from a chest in the dungeon and on that one the ingame description is correct and does tell you it’s worth 1s8c. I believe this is probably also the same with the Minor and Superior version, but I don’t have one of those so I can’t confirm it.