Sigil of Arcane Swiftness

High alchemy turns Sigil of Arcane Swiftness into 6,000 gp. Buying one at 50,000 gp (its guide price, as it has not traded today) and casting with a nature rune at 137 gp costs 50,137 gp. That is a loss of 44,137 gp per cast at its guide price, so it is not worth alching for profit right now.