more $$$ than new ones then if they're really broken in and sound so much better?

And if you say "they need to be broken in on the equipment you own", why would it physically matter?

used is used, new is new.

BTW, cars need to be broken in too. Shall I go on? :-)

The argument is that cables will perform at their best when the dielectric around the conductors is saturated with energy. Prior to this, the dielectric will absorb some of the energy and will re-release some of that energy back into the conductor, adding noise to the signal.

As the argument goes, this is why the best dielectric is none at all (ideally vacuum), or materials that have a lower absorption rate (i.e. teflon). You also get ideas like Audioquest's DBS system, that attaches batteries to the cables dielectric to keep the dielectric energized.

As to why a used cable doesn't cost more than a new one, it's because it doesn't take that long to energize a cable through use. It doesn't matter if it's on your system or someone else's, though the cable would revert to it's pre-energized state quickly.

Whether or not you buy into this is up to you, though I'd suggest a/b'ing some cables on a system you know well. My own experience says that cables do make a difference in a system, particularly one that is analogue based.

that's the whole point. a dialectric is made from a material with HUGE amounts of resistance.
also, people seem to be under the impression that a charge just hangs out inside of a cable on it's way down like some kind of garden hose full of electrons. there is nothing travelling through a cable, an electron is jammed into one end, and a chain reaction makes another electron come out the other end. very unlike the way cables are described in advertising.
electricity travels the path of least resistance, and a dialectric is nothing but resistance.
the only change a cable goes through is a slight molecular breakdown as the conducive metal is exposed to trace amounts of corrosives over time.
maybe rotting cables sound better, but dialectrics don't energize with anything but a trace magnetic field which is a reaction to signal, it does not act upon the signal.

You're assuming that what I wrote was an argument, which it wasn't, as I'm not an Engineer or Scientist with the expertise to authoritatively talk on the subject.

I can speak however to my own experience, which has been in the AV Industry for the past 12+ years. I have no problem saying that different cables have an impact on the overall sound of a system, though as I said before I'd suggest people listen for themselves, preferably on a system they know well (my system for example consists of Martin Logan speakers with a Meridian front end).

In terms of your reply to my post, I don't know how much energy it takes to electrify a dielectric, but Googling "Dielectric Constant" shows that different materials do have different values, i.e. Vacuum is rated a 1 at 20 degrees Celsius and Teflon rates a 2.1 (with other materials varying widely), so presumably not all dielectrics are the same. I'd also point out that we're not talking about a dielectric holding a charge for a long time, otherwise when you hit pause on your player you'd hear something, right? Rather we're discussing a theory that a dielectric can store and release energy back into a conductor in such a way that it audibly adds some distortion to the signal.

because even the worst dielectric has more resistance than your whole body. cable companies just say things because they know the avergae person won't know anything about it, and then when someone puts up an argument, it suddenly becomes a matter of opinion? it's not opinion, breaking in a cable DOES NOT affect the sound. i'm not giving that one the benefit of the doubt because there is no doubt.
and yes, there are dielectric values, but it doesn't mean alot when it comes to sub-ghz low gain signals. it's sort of like how dead you would be between a million ton weight being dropped on you, or a two million ton weight. either way you're burger.