There are cheaper S's you can find, yes. However those are likely AP1 models from earlier in 2016. Also, you're not getting FSD and unlimited free supercharging. Mine also has smart air suspension. It's also a 75 battery, just software locked. It's also still eligible to extend the warranty for another 14 months/30k miles.
i dont see how this is any different from buying at a traditional dealership. at least tesla tells you if the car has been previously repaired or not.
most dealers will just sell a damaged car as is and hope the customer dont know what to look for
i dont see the appeal as to why people prefer to buy from dealerships/tesla directly. it makes no sense to me why you would rather trust someone whose profession is to sale you something. i would rather buy from another normal joe that has owned the car and know more of the history.
Hard to know when you found an honest one. Private sellers, especially with Teslas, have a tendency to overvalue their cars and try to oversell features which may or may not hold any actual value.
From Tesla, the only real downside is that you cannot see/drive the car before buying, but you do get the full 4 year/50k miles warranty which will fix most issues. Also, I'd not expect a car from Tesla to be hiding any major problems.
On the other hand, Tesla stripped free supercharging from their used cars so there's that too. It comes down to personal preference and what one values more.
I'd also opt to buy from a private owner but I have yet to see a fairly valued one.