However...
Yes, in my heart I believe the tip and the shaft are the key to performance and the butt is mostly for show. (I will be honest here and say I have not owned many cues and I am not a great player. This is a belief on my part.)
However: consider the Meucci robot videos. Bob Meucci made those videos to showcase the black dot shaft, but the videos also illustrate that different butts perform differently with (supposedly) the "same shaft." Hmmm.
However, I suspect that the pins and joints are different for each cue, so there is no way to account for how much contribution they are having. Also, since the joints and pins are different, there was probably a different black dot shaft for each cue, too.
Just food for thought...
This is another argument for objective testing and performance parameters to cut through the marketing BS and player myths.