I popped over to their website out of curiosity. I don't there there is any way to determine the inductance as it would be conditional on how close or how far you kept the two conductors from each other. There width would negate some of the variability, but there will still be variability.
There is some contradiction in the statement below. I don't believe they have a metal alloy 33 times better than copper or silver (one does not exist), however, the claim below it compares it to a thickness of 5.5 times less. I don't see any particular benefit to a 0.00018 equivalent thickness of copper of silver. That is sufficient for about 200MHz back of envelope. It does sound impressive though. Any metal alloy with a skin depth of 5.5x that of copper or silver will unfortunately be a higher resistance alloy comparatively.
Since they are unlikely to have the resources to create their own alloy, I have to assume they are using something off the shelf. Monel and Constantan alloys are both up in the 5.5x range almost exactly and are Nickel/Copper alloys. However, they are really awful conductors. A pair of speaker cables could have resistance as much as 1 ohm. That would explain a unique sound.
FYI - materials science guy, semiconductors and batteries so this stuff is old hat for me.
The skin-effect characteristics of our state-of-the-art FIDELIUM alloy are up to 33 times superior to those of copper or silver. The FIDELIUM speaker cable, already at less than a thousandth of an inch thick, performs as if it were 5.5 times thinner, thus experiencing less frequency dependent attenuation and phase distortion than even a .00018 inch thick copper or silver ribbon or 64 gauge wire.