I would agree that no 2 cues would provide the same hit. So a custom maker will not able to 100% duplicate a previous cue.
However, that logic also applies to production cues, probably more so though, since Q&A is not as stringent.
I have had an opportunity to try many different cues, with many different shafts. I can honestly say, no two hit alike. some were similar, but not identical. I saw the biggest difference between the exact same model production cue. An schon Stl19, tried different shafts, between the two butts, and one hit great, and one hit hollow.
I have both production and custom in my case. I just picked up a Sugartree from Eric, a wrapless full splice with 2 shafts that is considerably cheaper than the P3 the OP mentioned. It is the best cue I ever hit with. I have let many people at the hall try it, and even people who swear by their preds, have said it hits better than their Icon, or sneaky, or thrones.
As for the cost argument, that falls short. You can get a great custom cue from reputable cuemaker for less than a lot of production cues. there is a Nitti for sale right now for $650 in the for sale forum. Point is there are really expensive production cues, and really expensive customs. There are also reasonably priced cues in both areas.
the people who say it boils down to the players preference and the cue they prefer are correct. Cost, custom, production, LD, solid maple ... all of it plays a role, but in the end if the player likes what they use then good on them.
I am glad the OP likes his Pred. I still think my new sugartree for less, is better though