Why do people want an earlier model year lower mileage car? Get a later model year higher mileage car. Means it was driven more often and didn't sit. That's what I would want. The ideal used M3 IMO is one with a good amount of highway miles on it. That way you can pile the miles on and not feel guilty, you get it cheaper, and it didn't sit in a garage. In terms of how "new" a car feels the build date matters far more than the mileage.
Sounds like a good deal OP. I am with the people whose first reaction is "that's cheap."