The warranty on the battery pack is 60 months / 60,000 miles. A replacement battery costs $5,500 plus taxes and labor. I wonder how many on Craigslist don't want to write that check.
A fair number of vehicles on Craigslist at the $10k price range have 20-40k miles on them. More than likely the battery will last 100k/10 years. Unlikely someone selling a leaf with 25k miles on it is doing so because they fear the replacement cost of a new battery.
Also, replacement battery costs are dropping year by year. So if one bought a used leaf, drove it for five years and replaced the battery you wouldn't pay $5500.
