In October '17, I bought a 2015 S with QC and 28,660 miles from https://nissanofportland.com/ for $9,325. Their original asking price was $12,000. I didn't show up at the dealer until I had communicated online with a salesman (woman) or two. When I got a sense that they might accept something in the $10-11K range, I drove up from Salem and offered $9K, fully prepared to walk. To my surprise, we worked our way to $9,350 without much back and forth. They even Ceritfied it, for what that's worth. It was a 12 bar car that showed 95% SOH on Leaf Spy. They currently have several 2015's in the high $12's. If my experience is any indication, you should be able to at least get $1,000 - $1,500 knocked off that price. I dealt with the sales manager, Jim Hamman.
http://plattauto.com/inventory/ has several mid 20K miles 2015 S w/ QC in the low $12's.
Good luck.