I sell my s7 at 1200 or so, means this price is only $2800. Works for me!
Can possibly sell the s9's at even higher profit and then just re-buy more A8's. It works both ways on the mining as well as ASIC selling.
Nobody mines with a single miner, dawg. Well, you do. But this also shouldn't be about some flee market shenanigans. Product at particular efficiency = appropriate price. That was very much the case with 741, taking into accordance quality. 821 is not that at all. Also see this post.