There is only one "good" (dubious) reason to by a really expensive cable, and that is for range. There is a performance differences between the cheap and gold cables, due to the different conductivities. However over short distance this isn't observable, as the receiver will correctly interpret the digital signal even though there is no noise on the line, this is the beauty of digital signals. It is there or it isn't, and with decent ECC on the line, which I'm assuming HDMI has, even with a fair bit of degradation it wont be an issue.
However as you extend the cable the signal with degrade at a different rate depending on the quality of the cable, and eventually you will reach a distance where the digital signal even with ECC is lost, and it will no longer work. With a higher quality cable this range is greater, (we are talking of ranges in the 10's -> 100's of meters), certainly no issue for a normal TV setup, and you would have to question why you even needed such a long cable to start with, move your source/receiver closer to each other.
The only other factor which might show up is the sensitivity and power of the transceivers, and you might find a cable of 100m works on some gear and not on others, but if you do you really are using the wrong tool for the job, go buy a optical repeater :)
I'm guessing on distances here, but you get the idea, I use to work in high frequency data transmission systems, and have no idea of the detailed specs of HDMI but should give you an idea.
There is only one "good" (dubious) reason to by a really expensive cable, and that is for range. There is a performance differences between the cheap and gold cables, due to the different conductivities. However over short distance this isn't observable, as the receiver will correctly interpret the digital signal even though there is no noise on the line, this is the beauty of digital signals. It is there or it isn't, and with decent ECC on the line, which I'm assuming HDMI has, even with a fair bit of degradation it wont be an issue.
However as you extend the cable the signal with degrade at a different rate depending on the quality of the cable, and eventually you will reach a distance where the digital signal even with ECC is lost, and it will no longer work. With a higher quality cable this range is greater, (we are talking of ranges in the 10's -> 100's of meters), certainly no issue for a normal TV setup, and you would have to question why you even needed such a long cable to start with, move your source/receiver closer to each other.
The only other factor which might show up is the sensitivity and power of the transceivers, and you might find a cable of 100m works on some gear and not on others, but if you do you really are using the wrong tool for the job, go buy a optical repeater :)
I'm guessing on distances here, but you get the idea, I use to work in high frequency data transmission systems, and have no idea of the detailed specs of HDMI but should give you an idea.