User pays makes sense...
...for the things you actually use.
But, in general, aviation regulation isn't for those that aviate (i.e. the regulated) as much as for the fare-paying public and the safety of the public at large.
Therefore "user pays" in terms of medicals oversight, licensing, some parts of ATC, security screening, ASIC's, maintenance regulatory oversight etc should be borne by the passengers and by the public at large. i.e. CASA's "cost-recovery" is a crock, IMO.
As far as landing charges, approach charges et al - these are revenue streams that are needed for aviation to physcially take place - I personally don't have an issue with them as such, except that the government has granted commerical relief to airport operators in terms of regulated land use and also an effective monopoly but also levies fuel tax to complicate this picture...