I completely agree. It's an arms race to be first. This latest $850 batch (to start shipping 8/24) will add several thousand more Z9 Mini's and will cause difficulty to explode at least 50% (is there a linear ratio between units put online and difficulty? I'm assuming that's the case), especially when combined with other manufacturers. Oops, also forgot the massive supply of Z9 'Maxi' units that deliver 40k (probably 60k when overclocked) that will hit in Sept.
Congrats on being nearly first. You should recover your investment and come out ahead (but you'll never make 400% ROI, with the massive difficulty increases coming soon). I was considering buying 1 or 2 Z9 Mini's, but it's gotta be too late now. I'd be one of the last to receive it (probably mid to end of Sept) and the difficulty will be at least 25-50% greater at that time.
Unlike other mining algos, with Equihash ZEC is the only 'real' coin that you can mine. ZenCash became unplayable once it suffered the dreaded '51% attack' - that coin can never be trusted again unless it hard forks to shut out ASICs. BTG forked to shut out ASICs, so HUSH is the only alternative and just 1 or 2 miners could completely take that one over making that coin unusable.
Bitmain can never be trusted. They secretly mine for weeks with new hardware to rake in the $, then finally dump them on the public once they cannibalize themselves. I don't believe a word they say when they attempt to deny 'secret mining' on their blog. As you stated, they dump thousands at a time at once, so unless you're first, you lose.
Kinda like the stock market - last one in loses. :-)
RE: Mining ZCash with the Antminer Z9 Mini - Part 4: Revenue data, pool switching and updated forecasts