While I agree with everything else in your post, the statement above is troubling me. It has to be a lot more than 7000 units in 60 days. Nvidia and AMD for example both produce millions of GPU's each month.

Lets do some research:
Bitmain's S9 production numbers are not truly known but we can make some educated guesses, we know for example that Bitmain is currently buying 100,000 ASIC chip wafers from TSMC monthly (source: https://www.digitimes.com/news/a20180130PD208.html?mod=3&q=TSMC).
You get roughly 5158 chips out of one wafer so at 189 chips per S9, that's 27 S9's per wafer (source: https://medium.com/@jimmysong/just-how-profitable-is-bitmain-a9df82c761a)
This means that with the 100,000 wafers they order each month, they can make 2.7 million S9's monthly!

I'm sure not all those chips/wafers are destined for S9's but it makes the 857,000 S9's over 60 days you calculated above sound much more plausible.