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
