I feel opposite; I bought two A3's for $980 each and expected a total loss on them, and sure enough they dropped to making $6/day before electrical, and now they are up to $15+ per day I am floored. If Sia keeps rising, who knows. The Halong units are actually more expensive per hash than the A3, Bitmain's next A3 batch is only $520 each which is much cheaper than the Halong per hash.
The difficulty will be such that at the point the $520 batch is done shipping, daily will be back down under $10. A rise in the coin value does help though.
(also if you held your earlier coins, you actually made a lot more than $6/day
)