64,
Short answer is, "whatever someone will pay". I'm only new to this snowcat problem, so I make no claims to be an authority. However my advice is worth what you are charged for it too.
My Bombardier 252 also has a Ford 300-6 drivetrain, but the end of the tranny is about it for Ford. Like most 30+ y.o. vehicles, that doesn't mean it is easy to source even engine parts. For instance, it's a 1978 model cat, but appears to have an earlier engine because it's got breaker points, which I believe the Ford auto engines didn't. It's also got a 'rebuild' tag on the block, so who knows??
But the differential in mine is decidedly NOT Ford. IIRC, the OC is Oliver-C_____ (as in tractors), but even this I'm pretty sketchy on.
So if one of these other guys writes that it's got expensive parts, and offers advice on how to go about confirming the condition, I'd guess it was hard-learned info on someone's part. Because of the price and scarcity of parts and the really high labor input on things like tracks, the current value probably ranges from scrap metal/parts cat on up. You can get the local scrap value from a recycler.
It might be wise to consider the condition you ultimately want it to be in and how much you'd have to spend to fix this one up that nicely. Don't buy a turd and expect to make money polishing it up. Like collector cars, it's probably cheaper to buy one someone has already fixed up than to do all that work yourself. But if you're comfortable with a "rat"-cat and this one is sound mechanically, then who cares how it looks and you might get a great deal on it. In that case, as close to scrap value as possible is ideal.