While the Thunderbolt interface has been around for little over a year now, the required cabling is still relatively expensive, with prices ranging between £35 and £50. Up until recently, Apple was the only one that sold the cables. Since then, other manufacturers have followed suit. While competition usually leads to a decrease in price, research by arstechnica indicated that there won't be any significant price drops anytime soon. The website claims that that prices of Thunderbolt cabling won't drop until early 2013.
One of the reasons that the cables are so expensive is the amount of copper that is used, as well as the implemented technology. At the moment, all Thunderbolt cables have one thing in common: they use the same transceiver chip, manufactured by Semtech (which was taken over by Genum in March). When creating this chip, silicon-germanium is used, which is an expensive semiconductor that is often used for telecom applications. Apart from the transceivers, both ends of the cables feature three more chips, including a micron controller and a power management chip. The last chip, a power regulator, passes a 3 volt data signal and a 15 volt power signal for devices without an external power supply. All these components are required to meet the bidirectional speed of 10 Gb/s that is specified for the Thunderbolt interface.
In future cables, this will change. Intersil is working on a technology that requires only two chips on either side of the cable and fuses the transceiver and micron controller into a single chip. The other chip will be a combination of the power regulator and power management chips. The new chips will be produced using a cheaper 40 nm CMOS process, which has better yields and thus lower production costs. This process also reduces heat production, meaning less cooling material is required in the cable plug. Lastly, a cable compensation technique is used which should guarantee the signal when using cheaper cabling as well.
As mentioned, Thunderbolt was mostly an Apple product until recently. In the future, the cheaper cables and the increased amount of products with a Thunderbolt interface, should make the standard accessible to everyone.