I've got a TE450 and pulled the battery and starter, 8 lbs. There are a few gears still in there and a spacer or two. For weight savings, nominal if that. I could feel it between my legs as I race a TC kicker only.
The kicker kit is about $300 now IIRC, they lowered the price last year or so??? You gotta pull the cover, the clutch, to totally remove the E-start the crank needs a spacer annd gear removal. There is pics of a kicker install at thumpertalk somewhere.
Right from the dealers! I've been eye'ing an 08 510SMR and told my dealer I'd want a kicker installed.....of course he asked 'why?' and my reply? 'Just in case, you never know!" Straight from the dealer, about 300.