For the love of all that is HDMI!
Right, a sticky may be in order here.
As someone who has spent 4 years working FFTs, DFTs and all other types of wave forms can we get one thing straight. HDMI is not digital. Its a digital interface which converts the signal to analogue to travel down the cable and then back again. In which case, in theory, it is susceptible to degredation like any other signal over length as the amplitude of the signal decreases.
HOWEVER: The amplitude frequency of the signal at Tx (Transmit) is quite large therefore meaning, as long as the cable fits snugly you'll get a signal at the Rx (Receive) which is exactly what was transmitted. Some interfaces (1.3a) also use error detection and correction to make sure the signal is accurate. This is all done before you can even blink.
So to summarise, the price of your cable will have no reflection on the signal quality you receive unless you are laying down some serious cable lengths and we're talking probably 20m +. The only price reflection point should be in the quality of the connectors and how snugly they fit in the port.