The crux of the matter is that miners are now in direct competition with the manufacturers. A game miners cannot win.
I bet it's ALL of them now mining first for 2 months and then selling off the equipment. SPondoolies, Bitmain, etc etc all figured out they can make a lot more money milking their machines first and then making even more dumping them on customers.
From what I read about Bitmain, they dumped all their leftover S2s into a data centre. So I cant see them selling those off anytime soon, not unless some other large mining operation makes a direct offer for the equipment. Still, they are showing at a steady 2% on the blockchain pie graph, so are in competition with their customers.