Well, astronomically high costs, goes directly to their pocket, so that doesn't need to be explained.
Usually with new mining machine in the market old model price goes down but if they starts from an already low point the people who wants to move from S7 to S9 will need to sell more S7 ghs for each S9 ghs.
Also usually after the initial "panic" sell prices of the old model goes down enough to become profitable again, even better than the new model.
That already happened with S5 when S7 was launched, of course this is just temporal, but you could get a big profit, specially if you can manipulate the market and knows when the artificial problems are going to start or end.
So your basing this off of the assumption that they are buying their own asset on the marketplace?
I've got a lot of reasons to believe this is what is happening. The market place is manipulated the same way as the bitcoin price is.
Just when new things happen, suddenly there is a major dump, which can't be a coincidence and in fact is the reason i Left hashnest.
The latest plummets in the market price are likely more due to the difficulty adjustments (mostly) upwards, and along with the BTC price, nearing the redemption period (set at 90% maintenance costs). Hashnest has already stated that S7 hashes won't be converted to S9's, like they did with the S5's to S7's. My guess is that the tighter it gets upon entering the redemption period, the more people tend to sell their S7 hashes while they still can before they get 'locked in'.