The quality of random no-brand audio cables, connectors, adapters etc. tends to be right-out atrocious. There's technically going to be metal in there but that "nice", thick headphone cable that came with those cheap headphones (and even some decent ones, like AKG K240s) is going to consist mostly of insulation, not conductors. Plastic is quite a bit cheaper than copper.

You can get ok jack adapters for 80ct but honestly I wouldn't trust that thing if I didn't trust Thomann. Usually I'd be looking for Rean when wanting a cheap one but they're apparently not in stock. And I kinda doubt Neutrik or Hicon even produce them if you're spending five bucks on a 3.5mm jack you're not using adapters, you're soldering the exact cable you need.

Oh. Back to resistance: Doesn't really matter audio quality doesn't care it's still the same AC signal just with less amplitude which you can fix with the volume knob, You're looking for impedance and material boundaries have a habit of being bad for it, as well as signal quality as parts of the signal will propagate through the boundary and parts will reflect. For more information ask an actual electrical engineer I merely wrote an A in a course I had to take and can tell the hot end of a soldering iron from the cold one (it's the one with the cable).