Well the good news is the starter clutch is...you guessed it about $100, but then while your in there, why not rebuild the solenoid...another $25...then you could rebuild the starter...i.e. clean and undercut the armature copper and mica insulators, (if after you test it on a "growler" to make sure no windings are shorted/open), and then the brushes and springs kit, another $25 or so...or replace the works for about $300...!
Given the choices and the age of the machine, I would go for brand new one...quite honestly you could also benefit that the new one has some updates to make it even more reliable (my sporty had 3 revision changes on the starter clutch, but the other parts remained unchanged and my Sporty is a 2004 (probably had the Rev B in it) so I went with the starter clutch replacement only.