Sigil of the Guardian Angel

High alchemy turns Sigil of the Guardian Angel into 18,000 gp. Buying one at 200,000 gp (its guide price, as it has not traded today) and casting with a nature rune at 137 gp costs 200,137 gp. That is a loss of 182,137 gp per cast at its guide price, so it is not worth alching for profit right now.