Is it the shaft or the butt? It's the shaft. Been shown countless times that the butt makes absolutely no difference in the playability of a cue. "Feel" is totally subjective. But you could thread a shaft onto a Szam or a broomstick, and the deflection and playing characteristics would be the same.
The cuemakers you mentioned have a reputation, the same way as classic cars are sought after. Legacy and nostalgia. Nothing more. Would I rather play with a Balabushka or a Schon? Hmm....Schon. Would I rather flip a Balabushka or a Schon? Balabushka. Because even though the Schon is made of better materials and has modern adhesives and finishes, there's a near infinite supply.
I think most of these cuemakers do not have a wait list of 5+ years because they make a superior cue to anyone else. It's simply supply, demand, and the principle of scarcity. That's all.
A Szam does not play better than a Predator. They just play different. And performance would be a subjective matter. If I like low deflection cues, the Szam would be a bad cue, according to me. The Predator would be great.
I also think Bob Meucci was the first guy to throw out the term "deflection" in the 80s. So I'm quite sure that the cuemakers of the 60s and 70s weren't even thinking of deflection when they made their cues.