I insured mine when I lived in NY because it was mandatory. If I remember correctly, it was somewhere in the $60-$80 per sled range, for liability only.
2004 Polaris Trail RMK 136
1997 Ski Doo Summit 500
2000 Arctic Cat ZL550 ESR (in NY)
2000 Arctic Cat 440 Panther (sold)
1980 Arctic Cat Jag 3000 F/C (in NY)
"If it ain't broke, take it apart and find out why!"