If it were a CA car it would easily be worth $6k or more. I don't know about how the potential rust issues in IL will affect things, but even then, I expect $4k and more, easily.

Check your local craigslist and pay attention to the cars that come and go quickly and the ones that stick on there forever. That can give you a clue to your market pricing.

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2001 X5 3.0i, 203k miles, AT, owned since 2014