Keep your eye on the evil auction site (epay). These come up from time to time when someone buys a pallet load of them from gov't planet or other auction sites, or if they cannibalize their broken gensets.
I found a good used starter for $85 and about $12 postage (IIRC), a NEW alternator for about $150 delivered.
Parts/spares are like that. When you REALLY need one, they're scarce, hard to find, but the Green Mountain Boys always have them for about twice what last month's market rate was.
If you buy spares when you don't NEED them, but have a few hundred dollars around, you can find them really cheap.
Good hunting (Weidmansheil!), the game is afoot. Shop victoriously!
Norm