Age is a massive factor, NCB + Age are the biggest factors within insruance.
This was just a test quote.
Me - 21 - SV650 - 2NCB - £415 Fully Comp
When I reach 21 I'll have 5years NCB so it will be alot cheaper.
It also depends on your bike, if I bought a GS650 they would lower it due to it being a "touring bike", if I where to buy a Mille or a ZX10 "Super Sports", it would be alot higher. They asses your bike on it's capablitlys, Sports Tourers are usually the one's in the middle and "Sit up-& Beg" Bikes, like your Naked SV's, Bandits, FZ6, YBR's & many more. They are your lower end insurance costs due to their style of riding.