Absolutely! I'm not letting it go, I just need to come up with a reasonable value.
Ask the soon to be ex how much she'll give you for it, to buy it from you. Maybe that would make your case on value. Or it would be enough to go buy another. Hopefully it would just get her to realize what you can really get for it.
Unfortunately in cases like this, NADA or Edmunds are usually the reference of choice, not reality, and I doubt either will help your position.