At the very least you should put "BMW" in the title of the ad, and probably just "1990 BMW 535i: $4000" a let it go at that. Leave the body of the ad to explain, not the title.
I think the price is pretty high but then I'm not in California. I don't know how much cheaper these cars can get though, but I'm even seeing quite a few E39s now around five-grand . . . with no body damage.