Neptune is not a competition right now because their 666GH box cost was $2000-2640 when ordered 7 mo ago.
If KnC will start selling it for 1BTC or 5BTC for the 3Th machine, then it is a different story, but it is not going to happen because they still have batch 1 and 2 to deliver in full, then in a month-batch 3 which is $6k for 3Th.