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.