New expensive power cord for amp and no change in sound?

"the amp’s manufacturer said don’t bother. "

If anyone should know, it's the manufacturer?

an amp I bought 2 years ago came with an expensive power cord (as a gift - the seller was getting rid of everything). I hear no difference whatsoever between it and regular power cords. I assume it depends on the components, if my amp and speakers were in the same class as the cord, I might hear the difference. 

If power cords really made a big difference wouldn't component manufacturers be putting better stock cords on?  Are there any component manufacturers that put anything other than standard plastic covered cords in the box?  

"I hear no change in the sound quality from a $500 cord"

"Did I throw away several thousand dollars?"

How does one throw away several thousands on a $500 cord? 

If you can't hear the differences, it's either 

1. You lack the critical ear to discern subtle differences

2. Your setup is not resolving enough

3. Your new cord is very similar to your previous

If you think it's 1, count your blessing and just enjoy the music.