Alex is right. I bought my 10ft Thunderbolt 2 cable from OWC (http://www.macsales.com) for under $30, the cheapest I’ve seen for a quality cable.
A word of warning against the longer Corning optical Thunderbolt cables: they don’t last and are very expensive. Check out the reviews on Amazon and other sellers and read up for yourself. Studios are spending upwards of $200 to put their computer further away from the interface and then the cable is failing in 6-18 months. These are installed, immobile cables and equipment with no abuse. My suspicion is that the circuitry inside the cable connector is overheating, not that the glass fiber is failing.