Hoping this is the right thread - here goes
I remember a bit from ch5's gadget show, the last series i think. Don't quote me exactly on this but they tried out 3 leads i think - a cheapo couple of quid one, a mid range £15 one , and a stupidly expensive £100 plus one. They tried each lead on the same player and same tv, put the tv's next to each other and couldn't make out any difference!
The only thing i would say is ( it isn't really relevant to hdmi leads due to their physical attributes) when it came to scart leads for example where i'm sure the same is true concerning quality and price, i would always steer clear of the mega cheap 'poundworld' type ones - purely due to the fact you could give them a little sqeeze and you could see that they weren't so well manufactures as the plug would deform and go out of shape. Then again as long as a pin goes in the right hole there's probably nothing to worry about.