Quite. Anything able to conduct enough that the other end can tell the difference between a '0' and a '1' should do, with the rider that HDMI at max resolution is damned high frequency, so "just" a piece of string won't cut it, and the longer the cable (10m+) the better it needs to be. Nonetheless, I run a projector at 1080p with a 10m cable that cost me a whole £9 including delivery (some years ago).
Gold doesn't oxidise, so an incredibly thin layer of it is used to provide a clean contact that never loses its conductivity and is the best thing for connectors and switch contacts in high-reliability applications. Domestically, non-plated contacts are more the norm (cheaper to make) and just means the user has to be aware that if something goes wrong you might only need to reseat the connectors.
It's the extreme audiophiles that go mad about cables, particularly the connection to the loud speakers. Granted the signal is analogue so the slightest disturbance to the linearity of the cable will convert to distortion in the sound, and the speaker cables may have to carry a high current, but $7000 per metre???
But you do have to remember that HDMI is digital (so if the system works, it works) whereas SCART is analogue (so it will work at varying degrees of quality), so a really cheap SCART cable could leave you with an unsatisfactory picture.