It doesn't matter about the rarity of the item, it's untradeable and serves no use as it's the equivalent to the Serp Helm anyway... It'd be a different story for instance you got a DFH from Mithril Dragons, for the obvious reasons it's tradeable and has value to it.
All a mutagen does is recolor the helm, and personally I'm not one of those simpletons who thinks cosmetically appealing = better.
Fire Capes, imbued items, Culinaromancer Gloves, Defenders, those are what would increase the price of a account