I have over 100 T9s running with zero failures so far. They clown on the S9 for reliability. IMO the efficiency trade-off is well worth it since its likely an S9 wont run problem free until you reach ROI and it looks like these T9s will.
I wonder whether the efficiency trade-off translates into selling used equipment from their own mine. The second hand equipment they gave me in replacement of my faulty boards was definitely from their mine,
but I wonder if they are selling second hand machines as new.
How long until you reach your ROI do you think? And how long have you been running your T9's?
Even in China, selling used anything as New violates the law. Sure that only really works for Chinese Nationals as far as prosecuting goes but it IS excellent grounds for FTC to bar imports so. Bottom line is no they don't/can't. For warranty replacement them using reworked/repaired boards is allowed and in fact is very commonplace throughout most electronics industries.
As for getting dirty/dusty miners... Ever been to any large city in Asia?
When it's dry they are often very dusty places. The miners are typically all burned in for at least 72hrs in open buildings. Dry out of the rain yes but sucking all that city air well you get the picture.
Just because it's law does not mean they adhere to it, I know many Chinese companies that use bitcoin to evade their taxes, so the law would appear to be relative in many cases. But either way, they are either selling a faulty product knowing that their customers are unlikely to even reach ROI, which is all kinds of wrong. Or they are selling second hand equipment from their own mine despite the law. I had around one third of my boards die within 2 weeks of operations, so one of my 2 scenarios is true.
And as for replacing warranty parts with second hand equipment, I have never received second hand equipment in replacement for broken electronic equipment. Even if it does happen a lot in Asia, it's still a bad practice and shows contempt towards the customer.