Typically you will see some variance in price depending on the company, but usually, they are in the same ballpark.  If you get a quote for $2000 a year and another for $1800 a year that's to be expected.  If you get one for $1,000, probably not.  There is usually something going on behind the scenes, like one agent or the other classified the policy incorrectly. There are different classifications on what they are insuring and it's up to the agent to determine the correct classifications.  Sometimes mistakes are made and they are not doing it the right way, but the best thing to do is ask questions.  

There are some carriers that have significantly lower premiums because of exclusions.  For example, we work with a carrier that has lower rates for one class code and they do so because it's for a very niche group of people that don't do this sort of work.  So, if you are not doing the type of work that is excluded, you can qualify for a lower rate class.