Restored, in working order and in a shop, I would expect to see machines of this era selling for $4-$500. Less condition, less value. They are a hard sell and restoring takes time and elbow grease, hence makes it even harder to make any money if selling.
At live auction, I see them sell for less than $100. They usually end up as plant stands or salvaged by the family because it was grandma's machine. Of course, being grandma's machine places a different value on it. Sentimental value, which is difficult to determine.