You’re kind of missing the point here. GAMI’s UL100 already works in all engines manufactured by Lycoming and Continental without any modifications. That includes the high compression and turbocharged big-bore engines that use most of the avgas anyway. Asking those users to spend tens of thousands of dollars to modify (derate) their engines to accept a lower grade fuel is a non-starter if they can use a 100 octane fuel that the manufacturers have already approved (which they have). Also, don’t forget that any modifications to current engines would require FAA approval through an STC process that would probably take years to accomplish. Why bother if there is an acceptable substitute fuel already available? And, don’t make the assumption that G100UL will forever be 50-80 cents per gallon more expensive that 100LL. Most refineries that do not produce leaded avgas don’t want the hassle and expense of producing a product that has to be religiously separated from all other products due to the lead. If they can produce something which does not require that amount of separation and recordkeeping, they may decide to get into the business. More competition would naturally result in lowered prices. That is one reason why Shell (among others) doesn’t want to switch away from leaded avgas. Follow the money.