there are many ways to make a cable, and sure enough some of those ways can change the sound audibly. braid it like mad to use 3 times the length of wire, cover it with enough shield to withstand an atomic blast, do something crazy between the - and the ground/shied, use ethernet wire, etc. at some point the sound might change and some might prefer it because they just paid 500$ for that crap and they were convinced the moment they paid for it.
now are those methods improvements? probably not. simply because the default cable in this specific case is a fine cable, they even bothered using 2+2 wires all the way until the jack for even lower crosstalk, and both sides are kept straight at a reasonable distance. given how inaudible crosstalk is unless it reaches something like -40db or so, we could even count that as already overkill(but cool for those who wish to re-terminate it to balance I guess).
so most likely anything sounding clearly different equals to lower fidelity. could be more euphonic, why not? but fidelity for a given reference can only have one sound and the default cable seems to offers close to it, so significant change can only mean one thing IMO.
the other question would be about the sound quality to $ ratio. is it expensive to make a cable with good electrical properties? no it isn't. a cable is a passive component, one of the most basic stuff in our sound system and has zero legitimate reason to cost as much or more than the headphone.
using silver instead of copper IMO only means an insignificant reduction in impedance that could be achieved just as well with a slightly bigger diameter of copper. and copper is more malleable than silver so I would always favor copper for stuff I will move around and bend a lot. but all in all it doesn't really matter, we're listening to music not trying to strangle werewolves. the HD650 is 300ohm and more, nobody cares that the cable is 0.5ohm or 1.5ohm. maybe the 20khz will end up 0.2db louder, big deal, is that worth spending 400$ in that expensive silver cable? because I can sell you a free EQ for 200$. great value!!!!!
litz stuff do have some benefits, but those benefits are located way outside of the audio range, and really make sense for high frequency signals, not much for analog audio.
cryo magic, well I won't insult you guys talking about that joke. half the time the properties claimed by those who promote such services don't even correspond to the proper metal.
so we're left with pretty stuff and soft touch cover around the cable, not sure that should cost hundreds of $, but beauty is in the eye of the listener ^_^.
