Well, I live in the Bay Area and have bought several used cars on Craig's List. If you change the search criteria to include only owner sale cars (no dealers) and go to the middle of the pack of cars left, you see prices about $7k. That is probably pretty close to what actual sales prices are, maybe a tad lower. Note that at least in the Bay Area there are quite a few amateur dealers that sell cars but list them as if they are individual car owners. I would be sure to take a LeafSpy dongle with me when looking at used Leafs (actually any used car).
In California, to register a used ICE car to a new owner requires a smog check. If the check engine light is on, the car is nearly impossible to sell, and it is well known that anyone can temporarily clear the check engine light by disconnecting the battery for a while. The DTC code reader (LeafSpy dongle) will tell me if there are "pending" DTC codes, which means the car will likely fail a smog check.