Well, when I make my own cables, I might get silver wire instead of copper (at least for the signal wire), which adds a few $. I think the various wire materials, and to a lesser extent, different dielectrics, do sound different. But I don't think a $300 silver cable is necessarily any better than the $50 silver cable I made myself.
So, it doesn't have to deplete your bank account. I think that within the people who buy crazy-expensive cables, there is something psychological at play, beyond just a belief that cables are not all identical. I think that belief, in itself, is pretty reasonable and not crazy. You can accept that, without going the extra step and swallowing the audiophile marketing kool-aid and believing that the more expensive a cable is, the better it must be.