92 dB at 30hz... even a Sonos Sub can do 99+ with higher WAF form factor
I think if this were a $700 to $800 sub, it would have more of a place as a price / performance value for those that absolutely wanted something this size and didn't need a lot of output.
But I'm sure they'll sell plenty to people who trust the KEF brand name about the specs, believe that a new technology is always better, and/or just want something to match their LS50 or LSX.
Many speaker brand manufacturers make subs that are way overpriced at full MSRP. Yet people buy them because they aesthetically match the main speakers.