Customs are different though, it's not just about fit. The drivers are positioned a certain way based on the shape of your ear, something you can't get with universals. Also burn in is not a myth, with iems and even cables there's a period of muddyness you experience before the sound opens up, a lot of electronics that produce sound go through this stage including things like speakers and tubes in guitar amps. I remember not too long ago people were saying that cable upgrades serve no purpose.
Yeah, I'm going to have to disagree on all three assertions based on my experiences, plus I'll throw in science on the cable and burn-in claims.

I did have the UM56 custom ear tips (lost them a while back) and couldn't recon much of a difference. But that is assuming I could get a great fit with the universal tips. If one can't, then I wholeheartedly agree then customs might be the way to go (except for the large loss in resale value thing
