Ivory wasn't cheap or readily available, at least not in pool ball grade. I read recently that the average tusk could only have two or three pool balls made from it. I would think ferrules would be the same, maybe a dozen or so out of a tusk. Pool was going through ivory at such a pace that a $10,000 reward was put up to find a substitute. Several nice discoveries were made before working materials were found. Ornamental grade ivory was readily available, "structural" for lack of a better word, ivory was much harder to come by.
One pool cue with ivory from end to end, ferrule, joint, and buttcap, might use all of the structural ivory in one tusk. This explains the price from quality suppliers and builders, and why so much modern ivory is unsuitable for structural components of cues.
Hu