If they are selling as “used” which means it has over a specific number of miles that precludes the dealer being able to classify as “new”, I’d just do the usual research to see if they’re in the ballpark. If they are selling as “new”, I’d just compare to others around the country but shoot for at least 5% to 8%...? Since it’s already a year old presumably, you can try looking a book values though they are certainly not exact or in some cases reality-based. Just my personal opinions! Others may have a more accurate take.doesn't it depend on the miles and condition? I doubt there's a fixed number.