I have been reading these posts on power cords for a while. As Snooker says, everyone has an opinion. I will make an analogy to an expensive bicycle; manufacturers will cut on the less noticed components (ie. seat post, bars, etc.) to maintain price points. In stereo equipment, one of these areas may be the power cord.
Although I am no expert, it seems the power cord has 2 primary functions, to transmit current and to keep out noise. Larger gauge wires carry more current. Better terminations on your cord (and a better wall outlet) should reduce losses and noise. Shielding and ferrite suppressors help keep out noise. I have one (somewhat) expensive power cord and it runs to my main 2-channel power amp, since the amp draws the most current. My other cords have been upgraded to Volex or Hubbel 14awg shielded cords with ferrite suppressors added. By going through an electronic supply outlet for both the cords and suppressors, the cost was relatively low (about $20 per cord). My next upgrade in this area will be having the electrical in my house upgraded with dedicated power lines for my stereo equipment. These upgrades have worked for my associated equipment. If you have an expensive system, you may notice a difference with better cords on all components (and don't forget the power conditioner - another thread!).