That is a different argument. The gains from going balanced can certainly be argued whether they make up the costs or not.
The OP is saying you can use a balanced amp just as well with only 3 conductors.
EDIT: Not defending balanced or not, headphones are much more sensitive than speakers.
Thanks for the clarification. The definition of balanced does not allow for just 3 conductors. Also, not to sound rude but I really could not understand what the OP was trying to get across.