From an electrical perspective the conductivity of gold and copper are not sufficiently different to make the investment in gold worth-while for audio frequency wire, either internal or interconnection. The only place where it might perceivably make a difference is in the ultra-fine windings of a moving coil cartridge. The same goes for silver.
However gold plating is used on connector terminals for the pragmatic reason that it does not oxidize and hence, if the plating is sufficiently deep, the connection will maintain long term integrity.
Where you see gold and silver used for wire you can be sure that the real reason is that the unscrupulous marketing turkeys are trying to sell expensive products to those people who are easily deluded.
Save your money : )