The difference in rates is in part due to how a Vstrom is classified. I work for a medium sized insurance company and have my house, cars and 1981 Honda CB750K insured through work. A few months ago when I bought my 08 DL650, I was told that they wouldn't insure it at all because the list they use classifies it as a sport bike. They don't insure sport bikes, they only insure motorcycles with side bags and windsheilds. I told them it had side bags and a windsheild and after I showed them a photograph, they decided they could cover it.
So, if an insurance company is charging too much for your Vstrom, find one that doesn't classify as a sport bike.