In most states/mfrs, here is how a "buyback" is calculated. It is based on the assumption that a car's life is 100,000 miles. It assumes you used up some of the car - even if it's unhappy miles, still you used some. So for simplicity's sake, if you went 10,000 miles they give you back 90% of everything out of pocket you have so far paid in.
2LT C7 Cyber/Red