Lightnings tend to be in the million$ plus range when they do come up for sale. I don't think you need to buy one of those to have the Vincent experience. In fact, for people who do spend over one million $ for a motorcycle, how likely is it that they will ride it, tour with it and really get some use from it?
When I was looking to purchase a twin in 2003, Rapides were in the 18,000 to 25,000 US$ range. Shadows were about 5K more. Now it seems Shadows are roughly double the price of a Rapide. That is a lot to pay for a name and some black paint, but obviously people are willing to do so.
A club member here recently invested over 100k in a cosmetically nice Shadow, then spent about 25k more to make it into a good runner. He already own a couple of Rapides and a Comet or three. He was grumbling about the cost of the Shadow then reasoned, " At least now when they ask if it is a G.D. Black Shadow, I can say, YES, IT IS!"
If you want a bike to ride, get one that is in the best mechanical condition possible. If your budget is stretched to purchase a Vincent, go for mechanical condition over rarity, matched numbers etc. That way you should have a bike that can do some miles for you right away.
If it is more an investment based purchase, then I dont know, one of the more rare models or at least a matchin numbers bike could go up more in value as a %than a mismatched Rapide or Comet.
On the other hand we might be at the Zenith of prices now and the lower priced models might not have quite so far to fall?
Glen