You can see this at work already with gasoline for small planes, which commands a huge premium over automotive gasoline now. Around here, the cost is 2x higher or more. The premium used to be smaller, but when gas prices came down from their $4 high, avgas didn't really follow.
87UL and 93UL aren't much more expensive than automotive gas, since it's pretty much the same thing. It's 100+ octane leaded gas that's expensive, and it'll stay that way until general aviation gets out of its carburetor & fixed timing rut and join the modern world of direct fuel injection and FADEC.
Which will not happen quickly because FAA certification makes re-powering small aircraft expensive and strict maintenance requirements keeps half century old planes running
