Now this is taking me way back and my memory is not the best.
The Schafer Ghost and Schafer Screaming Eagle I THINK were production bows patterned after the Silvertip but not made by Schafer. Martin may have been the manufacturer and the Screaming Eagle was sold by, well Screaming Eagle.
Value- subjective. If it feels, looks and shoots like a Silvertip and you plan on using it , probably a good deal. If you are looking at it for an "investment" I'm not so sure.
Others, please feel free to correct my info if not accurate. As I said this is my recollection and the accuracy may be off.