Sorry, HDMI runs at a maximum clock rate of about 340MHz. Inside that, there's a useful data transfer rate of about half that. That brings it into line with Cat5 cable, which costs about £50 for 305m on a one-off purchase (connectors and crimpers included).
Since then, there is Cat5e (which can handle Gigabit-rates), Cat6, and Cat6a (which can handle up to 10Gb Ethernet and potentially more). And these data rates are at **100m*** (or 50m, in the case of 10GbE), not the paltry interconnect distances between HDMI device. How much is Cat6 cable? About £50 for 305m.
So assuming you bought a 100m HDMI cable, assuming it was running at 1920×1200p60, assuming it has only 8 connectors on it (Cat5/6 only has eight wires inside, HDMI has more than twice that for little reason), assuming the quality of the connectors was better than some manually-crimped RJ45 plug, then it would be worth about £60 (£120 if you doubled all the connectors to make up for missing pins). For a two-metre HDMI cable? I'd expect to pay about 40p/80p - call it pound-store stock by the time you package it. Stick gold-plated (pointless) connectors on it and a bit of quality control and you're into the £5 range. There's zero reason for it to cost any more than that. Ethernet has been surpassing the datarates and requirements of HDMI for decades and in fact if you want to extend HDMI, you're expected to use CAT6-convertors/extenders for it.
There isn't nothing "special" in even the most expensive HDMI cable. Either something meets the HDMI specifications and can carry the logo, or it doesn't and can't - if it meets the specifications and is undamaged you will get a perfect digital image. There might be quality issues in terms of production (e.g. connectors falling off, conductors not taking kindly to right-angles and kinks, etc.) but in electrical terms HDMI cable is surpassed by the stuff that joins your printer to your wireless router (or whatever).
Even the analogue audio-cable scam was absolute rubbish. Digital signals, there's no excuse. I can't remember the last time I saw a packet re-transmit on my Ethernet statistics on any switch or computer I've managed in the last ten years - because it just doesn't happen when you cable and connectors and in spec. And my Ethernet sockets / plugs get more abuse than the average HDMI port - hell, they get plugged in and unplugged every single day into a dozen different devices and still work flawlessly. Unless you're rolling your chair over them, they work. HDMI is no different or more special just because it's carrying audio/video data. If the cable meets the spec, it meets the spec and can do 1920×1200p60, 4096×2160p24, or whatever the relevant spec revision states. If it doesn't meet the spec, it can't be called an HDMI cable.