I love how people like to twist words and meaning on this board. My point about race bikes adapted to street vs bikes made for the street and used in races still stands imo. Both a BMW M3 and Ariel Atom are street legal cars, but look at both and tell me which one was made for track first. Again, really it should come down to power vs weight if you are just considering the bike, given there is a much bigger difference in that ratio between a 250/300 and a 600/1000 SS. Also, should someone want to make a 300cc bike that can make say 60-70hp and only weigh 200 lbs, then that should be seen as a higher-risk vehicle in the same way a 400 lb bike making 120-140+ hp should.
I also tend to find it funny how the people who complain the most about SS insurance typically are the same who say a 600cc SS is too slow for the streets. In a fair word, insurance would be based on driver first and vehicle far second, to the point that if you are a new rider you should be paying a ton of money because you have no record/history. If you can get through a large number of years with no accidents and no major tickets, then insurance should be next to nothing until you do something that causes your record/history to change.