Erie ins. has been great for me price wise,not sure about how quick they handle claims because i never submitted one!I know when others quoted me $1200+,Erie got me full coverage on my 99' chevy for around $600,including commercial which was only $40 more,however my commercial has the same coverage as my regular policy,you may want more.
Low cost is the hard part. I just paid over 2k for my 88 F-350 for 1,000,000 liability and another 3k for general liability. It took me about 50 agents before anybody could even find the GL for under 20k so I consider myself lucky.
Try dryden mutual insurance company. They are out of dryden,NY. My agent is out of Glens Falls, NY. My landscapers policy is 1000 a year for million liability. If you want the number, I am at work now, I will post it if you want it.
Try State Farm...it took us awhile to find anyone who would even touch snow plowing insurance..but when we did the quotes we got were in the thousands.... then we found State Farm...their rate was fantastic and coverage is good...(this was for parking lot / driveway work...not roads...which were specifically not covered)