It will not be a lot when you get your learner's permit. Your parents will add you to their policy. Now when you get the actual license so that you can go out and burn up the highway on your own, yep, it'll be an arm and a leg. In a 300ZX that's a 1985, maybe not too bad.
If that car were new it would cost you a thousand bucks a month because statistics show that you're very likely to either get killed in it, kill someone else with it, or at least have a very expensive accident.
That's why, unless you're wealthy, it's best for young boys to start out with an old pickup truck, and that still isn't "cheap" on the insurance side.