That's true. It's hard to figure out what is "fair" in any situation. The problem I have is with people who think that GA should pay very little or nothing because the system is there for the airlines and GA only tags along. The reality is that there busy airports like KAPA and KPDK which exist only for the purpose of GA and others like KAUS which are shared by both. That's only considering ATC services. There are many other GA airports which receive federal funding for improvements.
ALL aviation benefits from government spending, BUT government realizes increased revenues in taxes generated by all aviation activity.
When government treats an airport as a revenue stream the airport dies. Case in point: Connellsville Airport.
The airport is owned by Fayette County. The attitude of the couty commissioners is that fuel will pay for the airport AND a whole mess of other things desired/required by the county (
eg General Fund).
After all, airplanes are for rich guys, right?
So no one flies to VVS for fuel, more hangars are used for cottage industries and car collections than airplanes, and the taxiways and rest of the infrastructure crumbles.
Just up the road another government owned airport sells fuel at competitive prices, maintains the field, and rents out a bunch of newly-built hangars.
There's a restaurant on the field, two FT mechanics, an EAA chapter, and lots of activity.
Build a toll road next to a freeway and guess which one has heavy traffic?
Now a fuel tax makes sense, but cannot be the sole source of revenue. Airplane mechanics, restaurant owners, avionics shops, and the rest dont pay fuel taxes, and yet benefit from the existence of aviation and airports.