There is a grain of salt for cables such as HDMI or other protocol-intense carrier. Altough Monster's claims are rather larger than life, HDMI cables are not regular coax cables. A nice benchmark is available here. The best cables are not necessarily the pricy ones, but depending on your application, some might not work well.
http://www.audioholics.com/education/cables/long-hdmi-cable-bench-tests.

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