Without any devices initially being available for it, Apple's Thunderbolt technology was relatively dormant in the public eye after its debut in the latest MacBook Pro and iMac systems. However, since the release of the Promise Pegasus RAID system, Apple's accompanying Thunderbolt cable, and some recent firmware updates for it, Thunderbolt appears to have caught a new wave of interest, particularly around the cable itself. People have wondered not only about its compatibility with Displayport (which has a similar connector as Thunderbolt), but also about its seemingly expensive $49 price tag.
iFixit today released a teardown of the cable to look at its components and in doing so revealed that the cable's unusually large connector jackets actually house a controller that is used to boost and condition the signal so it makes it from one end of the cable to another without any data loss.
Not only does the cable contain chips, but it contains a fair number of them. Each end of the cable contains six chips, with a large controller by gennum technologies, and a number of other smaller electrical components on printed circuit boards. Gennum technologies provides signal conditioning chips that allow for data transfer at high speeds. This technology appears to be the root of the cost for the cables.
As we mentioned in our, the raw components of cables can be a limiting factor for high-bandwith systems, and therefore will need to be made exceptionally well to handle the throughput. In order to get around needing to artfully craft each cable to work properly (which could boost the cost much higher than $50), Apple has included active electronics to compensate and manage the limits of the raw materials in the cable.
Because of the active components in the cable terminals, you might expect that with heavy use the ends may become noticeably warm to the touch. Apple initially mentioned this in their FAQ on the cables but later updated the article to remove the link to the page explaining the reason for the expected warm ends.