The Sheridan is great example of the oddness of collecting.

It began with the Model A. It was astounding, for the time, but did not sell well, because it was so novel and expensive.

So the Model B was a cheapened version, in order to sell better.

But it still did not sell well, leading rapidly to the further-cheapened but highly effective Model C that was produced from the 50s until the late 80s.

The oddness, as I understand it, is that the Model B now rivals the Model A in price - despite being "inferior", there were fewer of them made, so they sell for as much as the "better" earlier version.