Onyx necklace

High alchemy turns Onyx necklace into 120,600 gp. Buying one at 2,494,801 gp (its guide price, as it has not traded today) and casting with a nature rune at 138 gp costs 2,494,939 gp. That is a loss of 2,374,339 gp per cast at its guide price, so it is not worth alching for profit right now.