^ @2 + @4 : the cost difference between 99.5% and 99.9% pur…
^ @2 + @4 : the cost difference between 99.5% and 99.9% purity in vanadium for instance is >2x
^ @2 + @4 : the cost difference between 99.5% and 99.9% purity in vanadium for instance is >2x