Because it actually will cost around $300 per month for basic liability insurance on that car, that's why.
In many states, not being insured (under a personal auto policy) for a year or more can definitely affect your rates. The Las Vegas thing is also a factor, as is the Nevada thing. And while your credit score isn't a major factor, it's definitely a factor. The only time insurance companies don't use credit as a rating factor is in jurisdictions where they're prohibited by law from using it.
If one or two insurance companies are quoting really high prices, it's one or two insurance companies who charge too much. If they're all quoting high prices, it's you.