There are a number of factors that determine whether you are a higher, lower or average risk to an insurance company. Younger, less-experienced drivers under 25 cause many more accidents on average than other drivers, so they pay more. Some vehicles are more costly to repair or replace, or damage more easily. Some vehicle makes and models are stolen more frequently than others, thus they cost more to insure. Where you live.
Different cities have different theft and vandalism rates.
And, the bigger the city, the more accidents occur. Your own driving record. Years of experience, past accidents and tickets all count. If you're a good driver, your lack of accidents and tickets count in your favor.