Placebo effect maybe? Glad if you can post picture before & after changing the cable, so we can see the different.
If there is really a difference (if people say 0.0002% bit error), the effect is not sharper/blur. It will like intermittent/freeze picture just like astro effect during rain.
As for built material quality, that's for sure you can get better quality cable with those expensive cable, but not better PQ & perhaps may last longer.
Btw i'm still using byond HDMI cable with superb PQ (only on HD channel of course) & another extra HDMI cable (3m cable bought from Tesco for RM27 - decent cable looks) which i use to connect to my laptop when i need to play downloaded mkv movie.

Read this

CNET strongly recommends cheap HDMI cables widely available from online retailers instead of the expensive counterparts sold in your local electronics store

Quick Guide: HDMI and HDMI cables

You should post your problem here rather than this topic
Quick guide: change your default audio playback devices

For that price, I can get 25 pcs from Tesco
Try at lelong for bidding, maybe someone there willing to bid

You might be right on audio part.
I just wonder is that a noticeable different if there's bit error in audio? For video, most of the time we can see it.