I have 2 bikes, a 1980 Kawasaki KZ750 and a 2005 Suzuki S83 and they cost me $114 each per year to insure with just liability through Wawenesa. Neither are classed as "sport bikes" although in 1980 that KZ750 was one of the fastest 750's around and its still a really fun bike to ride.
Wawenesa has rules with their insurance if you want the really cheap rates, like no bikes over 600 cc in the first three years of your license,etc and I believe they won't even insure bikes like ninjas period. Their coverage suits my needs well right now though.