I'd completely agree, I've been in the RF Engineering world most of my working career (16 years). I nearly fell off my chair when I saw the prices of the Monster Cables in Retail Stores.
Admittedly I did buy one out of curiosity, and also bought a Rocketfish HDMI off eBay (for a lot less than the Retail Prices in shops), and a HDMI cable from a friend of a friends computer shop. The price difference between the 3 being from $150 to $25(including p&p) and $15.
I can't see any difference whatsoever between the 3, I played a movie and fixed on a certain area, then would swap the cable and compare. I don't know which of my Shaw HD PVR, Phillips Upconverter or HD DVD player has which cable right now, and I'm not concerned either.
It all boils down to marketing, Monster did a really good job convincing people that they absolutely must have these cables to get the best quality picture they can get, and back it up with technical jargon on the packet that most people wouldn't understand, and because they don't understand it, and because the cable is so expensive, it must be true (members of this board exempt of course) I'll bet most people who don't frequent boards like this, if you asked them to name a brand name HDMI cable, Monster would be right up there. It also doesn't help that some stores sell Cable Company HD PVR's, with no Component or audio cables that were supplied in the box, and then recommending a selection of Monster Cables that just happen to be in the store. I've come across that on more than one occasion, and don't agree with it one bit, yet because of the commision mark ups, can understand why they do it.