This may seem a bit unrelated, but I just have to ask, why are models/series of miners with high failure rates still kept in the market? and how come people still purchase them even with their bad reviews?
If you see those miners on the marketplace they are used units Bitmain is no longer producing old units like s17/t17.
If you found them on the marketplace those are not brandnew and some of them are not 100% working.
There are many reasons why people still buy them he might be a newbie, cheap or to learn about mining or maybe they know how to repair them and make a profit.
price and efficient may push one to buying the s17 pro
an s17 pro on a proper down clock may be able to do 1000 watts and 40th this may be attractive to some miners.
vs the new avalon a1166 doing 81th and 3400 watts.
they can be very close in price. and if your power is a bit costly you may 'gamble' and buy the s17
the op said they are able to have dirt cheap power if I were him I would push him at the a1166 gear.
but if he was at 7-9 cent power I may tell him take a shot on the s17
I have owned both and can say the avalon is better at not breaking.