Having been in the cable design and manufacturing business dating all the way back to 1986 as the co-founder of 2 cable companies, I can say that yes differences in materials and manufacturing will affect performance, especially at higher speeds, BUT quality cables do not cost much more than a lesser quality cable as much as some of the "high end" suppliers would have you believe. Monster does make quality products, but so do alot of other companies. Our customers were all the major OEMs, Sun, HP, Compaq, Apple, Sony, Avaya, Cisco etc. and I guarantee they do not pay for perceived quality based upon price. Belkin would probably be a good baseline for quaility products at a reasonable price. Most of Monster's cost is in packaging and marketing... not materials or manufacturing.
I am a 25-year veteran of the broadcast and audio/visual industry. I've been observing the deal with Monster Cable, ever since it came out. The answer between me and my colleagues is simple: People are stupid...and no matter what you tell them they will continue to be stupid. I remember back in the early 90s, when Monster made only their overpriced speaker cable. I colleague of mine who had a pretty heavy-duty electronics shop in his business. They did a very complete "sweep" of the cable and they found that any difference in quality was neglibile, and essentially nullified by commonly bad installation, lousy equipment, poor signal management, and improper use. It's prettymuch the same way today.
Monster resorts to a commonly used practice known as "specs-manship". If you can prove on paper that your product performs in a certain way, under certain circumstances (usually in a laboratory environment), you can claim superior performance and a resulting premium market price. Total nonsense. Lordargent made an accurate statement in the prior posting: "Who uses 33 feet of cable?" Most people need about 5 feet. I recently outfitted my masterbedroom with a nice Sharp Aquos 1080p LCD with all the trimmings. I balked at the non-sensical price of Monster Cable. Instead, I purchased some $7 HDMI cables online. They work perfectly. No artifacting...no dropouts. Oh yeah...and for anyone who talks about Monster having greater "clarity", tell them to get their head examined! Just as we discovered in the 90s that Monster speaker cable produced frequency performance advantages that were beyond the physical capabilities of most people to hear, if you can see bit-related errors from an HDMI signal, you need to get a job with the circus.
All kidding aside, here is my advice. Go to a retailer, buy the cheapest one, if it doesn't work, take it back and get the next better product. (For HDMI cables at Best Buy, this means you have three levels of pricing choice for the same type of product.)