An HDMI cable carries digital data, so it either works perfectly or doesn't work at all. You don't pay extra for gold connectors on USB cables or network cables, either.
FYI- most people probably already know this but you should pretty much buy the cheapest HDMI cable you can. No difference in quality. They work or they don't.
But what about the gold plated connections?!
As an Electrical Engineer perhaps I can elaborate.
High-quality connectors are important for analog signals - where the information is transmitted as an electrical "wave" where the amplitude (height), frequency (length), and exact shape of the wave all carry information that must be retained in order to reproduce the original signal most accurately. Bad connectors / cables can affect analog signals either by smoothing out things that should not be smoothed out or by adding noise that introduce things that were not originally there. Either way this would make the received signal not quite the same as the transmitted signal, which will lower the quality of the reproduction. Examples of information stored or transmitted analogly are vinyl records, old-style TV channels, the RCA cable format, and two-wire speaker cables.
Digital signals transmit information differently. On digital signals information is transmitted either as a high voltage, a "1", or a low voltage, a "0". There must be some form of tiny computer at each end to encode / decode the information into / from the stream of 1's and 0's. There can be almost any amount of noise introduced along the way; as long as the receiving computer is able to distinguish between a 1 or a 0 then no information is lost or added. High-quality connectors and cables are not important for digital signals; either the amount of noise is large enough that it overwrites the signal (in which case nothing will work) or it's not (in which case everything will work perfectly). Examples of digital signals are CD / DVD / Blu-ray, HDMI or DVI cables, digital TV channels, USB, Ethernet, optical sound cables, and pretty much every other form of computer cable.
This is why CDs do not wear down and their sound quality doesn't degrade over time, like records do. Either the CD perfectly (up to the format's limits) reproduces the sound or it's scratched and can't be read at all. Either the video / sound quality from a digital TV channel is perfect, or it's completely messed up as long as the branch (or whatever) is blocking the signal. There's no fuzzy sound or fuzzy picture like their use to be for analog TV channels with less-than-perfect reception.
If a $5 HDMI cable works at all then it will produce exactly the same picture quality as a $100 HDMI cable. The marketing people are merely lying and scamming you. This is why James Randi is offering $1 Million to anyone who can demonstrate the superiority of their expensive digital cables over cheap ones, and why no one has taken him up on it yet.