If you wanted to use Thunderbolt devices with your Mac, previously it was necessary to purchase one of Apple's Thunderbolt cables, which at nearly $50 each may seem outrageously expensive. Until now Apple's cables have been the only option, but accessory company Elgato has recently begun selling a Thunderbolt cable of its own. However, while third-party options often have the advantage of a lower price, Elgato's cable is currently no cheaper than Apple's.
The Thunderbolt technology introduced in Apple's latest Mac models provides exceptionally fast I/O, in its current form allowing up to 10Gbps bidirectional transfer between devices, significantly beyond the bottlenecks for technology such as USB and FireWire.
Unfortunately, the technology isn't widely used yet (though recently Intel has announced efforts to increase Thunderbolt adoption), and part of the reason has been the expensiveness of the devices on the market, with one of the most notable being Apple's Thunderbolt cable at $49.
Part of the justification for such an expensive cable is that in order to maintain the high bandwidth in the cable, Apple has needed to implement active electronics to stabilize and condition the signal. While Thunderbolt could maintain connectivity using a cable without such electronics, interference and attenuation of the signal over the distance in the cable would result in degraded performance that would limit bandwidth.
Even though the use of active electronics helped justify the $49 price tag of the 6-foot cable, as with other Apple products it was hoped that third-party developers would create offerings of their own at far lower prices, even if quality needed to be sacrificed a little.
However, Elgato's Thunderbolt cable is unfortunately inferior to Apple's in two ways. First, the cable is only 2 feet long. While this may be appealing to some who plan to keep the Thunderbolt device and computer close together, overall it's more limiting. The second fact is that Elgato's Thunderbolt cable will cost $10 more than Apple's, at $59 each. Elgato does offer an incentive, though, by bundling it with Elgato's external Thunderbolt SSD drive.
So far there are no benchmarks for any performance differences between the two cables, but the difference is likely negligible.
The good news about the release of Elgato's cable is that it lends credit to Intel's announcement that by the end of this year we should see an increase in Thunderbolt devices. Hopefully as these devices become more plentiful, their prices and those of the cables used to interconnect them will drop.