Well, I think you have never compared both, you just say what you think.
No, I have. I've played both standard and custom shop guitars from several different companies, including ESP (as well as Jackson, Charvel, Gibson, and Fender). In the case of ESP, I have also been lucky enough to play several Edwards (and LTD).
There IS a difference, no matter the product, from a musical instrument to a car. How big of a difference will depend on the person, but there most certainly is one. A whole industry (spanning more than just guitars) isn't based off of a mental placebo effect of simply thinking something is better because it's custom (even if some people do).
In a live setting, like at shows, it won't be as clear of a difference (in sound). However, it's particularly noticeable in recording. That's why all kinds of bands will specifically rent out extremely nice guitars, usually for at least doubling if not more. Same goes for amps and other gear as well.
Although there is too much fuss about CS guitars, I have to agree with Delanoir.
Even IF the materials are the same (what is not the case by the way, since the builders at the CS select the best pieces of the wood type you want) it still matters HOW they treat the wood. They can pay much more attention to tiny details than the machines in mass production do.
It may not be a difference which would justify 3000 Euros more, but it's probably there.
Exactly, thank you.
Like I kept saying, they're all great in the case of ESP (especially Edwards), and it isn't necessarily worth all the extra money, but they are better. I mean, after all, endorsed artists get (at least) a discount anyway, so they don't pay for it as much. And they're the ones who use CS guitars far more often.