I don't see a problem with letting it live. It clearly thrived enough to grow to an adult and it doesn't know its different than all the other fish. LOL
Same as Siamese twins in humans.
But I do have a huge problem with the fact they increased the price because its mutated.
what it lived to a adult i dont think so
please post a pic of any 2 headed aro at 2-3ft
the bottom aro in that video is just a parasite
if it was doing well both top and bottom aro would be the same size