Besides the gauge, the material is also very important. In terms of conductivity and price, platinum > gold > silver > copper. Some ultra expensive speaker cables do use platinum and gold and you can imagine the sky-high price.
However, some expensive cables (>$1000) still use copper (so called 99.999% pure). They can never be 10 times better than a generic copper cable with the same gauge for less than $100.
One practical approach is to buy an expensive cable/component ONLY if you can hear the difference.
