On outlets (to JLM's point)....the hospital grade 8300 outlets at Lowe's for $9.00 was a quality step up (one that you can hear) from the $0.39 outlet there originally. Since moving on to PS Audio and Porter Port fancier outlets....I hear
no further benefits
On power cords....the benefits are even more difficult to define or assign value based on money sent on them. If you're near a significantly busy source of Radio Frequencies (RF) and ElectroMagnetic (EM) Interferences (I)....well shielded power cords are a great upgrade. As time goes on in life, with the proliferation of radio, tc, cell towers, cordless phones, bluetooth, home/business routers and your equipment itself, good shielded power cords are probably more and more beneficial than they were 10/20/30 years ago.
But, you don't
have to pay $500 for good shielding, high purity copper, and a low inductance design. Cryo'ed, teflon tubes, silver, and fancy connectors may indeed improve the signal transfer further...but you pay a lot more for these fancy add-ons.
Good luck - it's quite a cable jungle out there

John