Carbon neutral synthetic fuels might make sense for airliners, because they're already pretty efficient, reliable and incomprehensibly powerful and there's tons of other stuff in them that'd require maintenance even if you took out the engines.
They don't make sense for general aviation planes that are usually a fifty year-old engine design that requires expensive overhauls and guzzles expensive fuel wrapped in a bit of aluminum.
But do we really need to focus on general aviation? I don't have numbers but believe it to be a pretty small part overall. In transportation, it's also fine if we keep some gasoline speciality vehicles for a long time, as long as we're able to convert the vast majority of cars and trucks.
Compated to jet fuel, avgas is more expensive today because there's almost no market for it. When synthesized, it's probably cheaper to produce than jet fuel.
They don't make sense for general aviation planes that are usually a fifty year-old engine design that requires expensive overhauls and guzzles expensive fuel wrapped in a bit of aluminum.