Yeah, there isn't a whole lot of rhyme or reason for some prices. Part of it is that non-harley bikes can drop so fast in resale that a person can get a bike from the 90s for 12-1500. Given that. most people going to think "why get an older bike for the same price". Part of it is poor info on what is actually "high" miles on a bike. Some think that number is as low as 20,000. Yes, crazy, I know.
So then with older bikes, it comes down to a person really liking that style and wanting that year.
That is just my thoughts on it. Makes sense but who knows for sure. And why harleys dodge this, I'll never know. They sure aren't any better than our bikes. Hell, my 78 will still corner, stop, and accelerate about as good and most of the harleys out there. All comes down to image I suppose.
The ride IS the adventure. The destination is just to get gas!