This is interesting, but I'll believe it when I see it. Right now, in Michigan, premium fuel is about 28% more costly than regular. Even if the 20% greater fuel economy is accurate, I'm not about to pay 28% more to get a 20% boost. Of course, I understand that if the ONLY fuel available would be 100 octane, or 110, the pricing picture might change quite a bit.
100 octane and greater fuels are available now. Sunoco 260GT (100 Octane) is available locally for about $10 per gallon. Though not legal for use as an on-road fuel, it was once common for some automotive restorers to use AvGas 100LL, (aviation fuel) locally about $7.78 per gallon. The bottom line is octane is costly today. Very costly.
I do know that my Pagoda really does not like regular fuel, and prefers the premium. One of my other cars is a high performance Ford Taurus SHO. I've used both regular and premium in that, and without some kind of instrumented, scientific testing there's no perceptible difference in performance (thought the HP rating is best with the premium) nor in MPG. There's a a realtime fuel MPG meter and environmental conditions make more of an effect than anything else; speed, weight, weather, etc. Thus that is always fueled with the lowest-cost gasoline available. The Pagoda is always fueled with the highest octane available at normal stations.