This is not really true, depending on your setup the more expensive cables do make a difference. You'll only start noticing it once your setup starts costing R60k+ though, and even more so when you go over the R150k line.
For normal average Joe use I agree, anything will do, but there is a reason you get HDMI cables in excess of R1000 a pop.
No way.
There is zero chance you can tell the difference between two working cables of the same standard.
Edit: By standard, I mean version (1.2, 1.3, 1.4 etc)