Zack/Gibson, Ritchie/Fender, Kirk and James/Esp, and all the others out there sign on with a major guitar manufacturer, and then work with usually a team of specialists to design their guitars to their specific specs. For example, when George Lynch first started working with ESP, he had close to 15 guitars made exactly to his specs. He then tweaked with each and every one until he got what he wanted. Your every day consumer can go to a music dealer, and buy an ESP made exactly like Georges. Same woods, same pickups and all. However, since 15 guitars all made to the exact same specs with the same parts will all play and sound differently, there's no guarantee that you'll get the exact same guitar.
I think it's pretty much the same in the cue endorsement world. Earl plays with a cue tec that is readily available to the average consumer, but I assure you that Earl was most likey worked with Cuetec reps, and tried several different cues of possibly the exact same design and materials to find exactly what he wanted.
I've played both Charlie Williams and Johnny Archer here in Japan, and because both times, I was one of the only English speaking guys around, I was fortunate enough to spend a little bit of time with both of them. Charlie played with a hand selected Predator, and Johnny played with a selected Scorpion.
I lost to Charlie 7-5. We then switched cues for fun, and he then whipped on me 7-2 using my cue with considerably more deflection than what he's used to when using his Predator. Sure, these guys have their preferences, but can pretty much make the adjustment to anything.
dave