DMV will come up with its own value now, so even you say it is free, the buyer still need to pay sales tax during registration. My guess the DMV system value is around 70% of KBB bluebook private party value.
By the way, you need to fill out a form and signed by the buyer to notify DMV you have sold this car, you are no longer liable for this car. Keep a copy of the form. The form number is stated on the title, you can download it online. Good luck
