Buy the cheapest. It's won't make any difference. Mine cost the equiivalent £5 at Conrad electronics and I see nothing resembling digital artifacts on screen. the build quality of the cable is actually very impressive.
The only case where you might want to pay more is for long cable runs.
The confusion arises from the very early days of digital audio when you might have had a separate digital to analogue converter (DAC) and poor cables could cause timing problems. This hasn't been a real problem for decades as signals are buffed and re-clocked into the DAC. Gramophone magazine once replaced a digital interconnect with bell wire and no one in a blind test could hear the difference.
As has been already said the protocol by which HDMI is sent is encoded with error checking and is also buffered and reclocked at the TV end. If there is a problem you will see "sparklies".
It's a rip off, the retailers are cashing in on public ignorance. I had to go to an electronics store for a basic, cheap cable (equivalent to
Maplin), all the electrical goods stores only stocked cables costing 4 times or more.