I think this talk of insurance really depends on where you live. I got a convertible corvette at 17 (an old one, but still...), and only paid about $70/month in insurance for full coverage. That was in northern California not too long ago. It helps to go on your parents' policy. Even if you don't live with them, you can probably still get away with it if you're a student. I did.
In contrast, I later moved to PA and bought an old underpowered benz worth 1/3 what the vette was. That cost $120/month to insure
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By the way, I got the Corvette for less than $9k. There are a lot of nice cars out there in that price range. You might want to check out things like Miatas and MR-2's as well (maybe you want something more practical?).