My gut feeling is no one would be able to hear the difference between a $3 standard house outlet and a $300 audiophile plug. Just saying......"bigtwin"
If you had read my 1st post you would have learned that I heard a difference when testing 4 different plugs from a low of $25 to a middle price of $150 , aural memory is short so to test 4 outlets they were placed in a 4 gang box , so after the amp was warmed up for 1/2 hour i would play a song , turn the amp off and plug into another outlet and repeat after testing all 4 outlets I tried a different song and repeated , this was done along with a professional guitar player whose hearing is way better than mine and we both could hear differences .
We both use AudioQuest , that's not to say that Furutech or Oyaide aren't better but we weren't out ot test outlets , we just used what we had around , the PS Audio now sends Ac to my TV .
A firm contact is important but the purity of the copper , the platings also make a difference , one you can hear .