Re: [25+PH] Kano CKPool kano.is 0.9% PPLNS US,DE,SG,JP,NL,NYA
...The only real advantage of the S9 is its resale value, which for some inexplicable reason is still very high...
Unless you're dying and need quick liquidation or a more efficient model comes out, who cares about resale value? 
I'm pretty sure there are more than just those two reasons for reselling miners
When the resale value exceeds the reasonable expectation of what you can possibly mine with the device - you should get rid of it (or not buy it to begin with) - wouldn't you agree? Unless it's a hobby. In which case none of the ROI talk matters anyway.