Bitmain would NEVER sell S4s at a loss because... wait for it...they don't have too.
If they price the S4 so they make a healthy profit on each unit but it's too expensive for home miners, they won't sell many at retail. But they'll just mine with them or add them to Hashnest.
And remember, their costs to mine with their own equipment is much lower than home miners who pay retail and don't have access to cheap power. They will be able to run them for a very long time before they become unprofitable.
This is pretty much what the s-4 is doing now mining.
Based on the s2 being roughly 55% the power per watt of the s-1.
the s4 may be under .5 watts or under 1000 watts per 2th.
They will mine them night and day right now diff is up 20%.
I would guess 1/2 of that 40ph in gear jump is an s-4 farm mining like a mofo
1 x s-4 = 2th
10 x s-4 = 20th
100 x s-4 = 200th
1000 x s-4 = 2 ph
10000 x s-4 = 20ph
they have sold 3000 unit batches of s-3's as shown in the btc chain
they may have 1,000-10,000 s-4's mining as I type. As it is a dense machine 1000 is not a problem to put In a large building 10000 not sure.