I'm all for buying things as cheap as possible. I too wondered about this, so I just bought/borrowed a couple different cables in different price ranges, and I do find that you have to spend lots of cash to get the 'ultimate' performance. If you want excellent performance the cost drops sharply. There are also instances where the 'expensive' characteristics of the cable you are buying do not benefit your system. For example, the transparency of a $1500 nordost cable does not really show enough benefit over a $250 truthlink with a vandersteen speaker because their inherently lower resolution (vandersteens make up for it in other ways) verses an audio physic speaker.
If you are building a very expensive, ultra high resolution system, you can hear the difference. They are there, and I'm not the only one who hears them.
As examples, my nordost spm cables sound more detailed than my nordost red dawn's, my (former) truthlinks, and the audioquest quartz cables I tried. All these cables were in the same general shooting range, but the spms were unquestionably better. I also tried some generic thick copper intereconnects, some $70 esoteric audio cables, and some mit 330's. All of these were a significant downgrade to the prior group.
On top of this, I tried my spm cables against the $8500 per interconnect Transparent Ref cable in my friends $70,000 system with all BAT electronics, SACD and Wilson Watts. We could both hear the transparent cable was better. No question about it.
I spent about $1500 (used cost) for my system's cables (2 red dawns, an spm, and oval 9s). I would rather it were $500, but honestly it would drop my system performance by too much. No question about it.