Depends. Most of the time headbands and pads are worn out on used ones. I have gotten some used in great shape that I’ve just cleaned and been fine with.

Makes perfect sense. How do you go about cleaning them?

It really depends how worn things are, and is gut checked against my personal tolerances for hygiene.

With leather earpads, it's not nearly as big of a deal, to me, and I usually just do a quick surface wipe with slightly diluted rubbing alcohol. However, for velour-type of pads, I check to see just how grimy things are, but usually have new replacements ready to go.

As far as cables, most headphones tend to use standard connectors, so I've amassed a small collection of random cables over the years that are bound to fit something, so it's a wash for me. Because of this, I tend to ignore any stock cables, unless of course it is non-removable. :P

Regarding headbands, sometimes there isn't much you can do about them. However, with Sennheisers (and I believe Beyerdynamics), there is an assortment of parts available for replacements on the market. Recently, I finally got tired of the super worn out/loose HD580's stock headband (which, has likely seen well over two decades of usage before I inherited them), so I ended up replacing it with a modern HD650's headband instead, as well as the plastic grilles at the same time. To me, they look so much better now, and no longer slide off my head, which is a win-win in my book.

Depends on the fabric.

Dawn dish soap and a toothbrush works wonders

It really depends. Sometimes the pads aren't really worn at all, but I'll still replace them because someone else was using them. The one exception to this would be genuine leather pads since you can just wipe those down with alcohol wipes and they'll basically be as good as new

Good info. Ty

I usually swap pads at least, if possible. But most used headphones that I’ve bought were vintage and needed repairs or replacement parts anyways.