Look under photographic equipment, and do a search for Cine Kodak or Cine Kodak 8, then go to the link to Completed Auctions. That should give you an idea what to expect. They were made from 1932 until about 1947, and are quite common. Of the three, they exist in ascending order of scarcity, i.e., the model 60 being least availble, the model 20 the most. But that's in purely relative terms.
None are hard to find.
Ebay might be a good place to look for current prices and sellability. Look under photographic equipment, and do a search for Cine Kodak or Cine Kodak 8, then go to the link to Completed Auctions. That should give you an idea what to expect.