Ferris: Revenue is collected from GA in a number of ways: The federales collect a tax on aviation fuel and on parts and appliances (any aircraft spare parts, new radios, tires, and other aircraft peculiar stuff etc) as well as a tax on airline tickets and freight waybills that gets money from airline passengers and freignt shippers. Airports are also allowed to collect money from GA in the form of landing fees and this is on a case by case basis. Most small airports don't bother or don't bother if you buy gas their or RON. Some big airports that have landing fees don't bother if you are a transient one time only light GA aircraft.
As far as inspectors to catch scud runners sounds like a typical European solution. Actually a European named Darwin figured out how to stop this without any significant new expenditure of resources for inspectors and various other nannys to babysit everyone. You scud run long enough you will kill yourself. Then you won't scud run anymore. Simple. But do it befoer you have kids and it will improve the gene pool too.