Dick CASA costs are small compared to the cost of operating at one of the privatised airports, costs which are not only direct in rents, landing fees etc but also indirect, passed on by maintenance organisations etc as they have massive rents to pay. Pus of course the location specific charging by Airservices.
If you could use your considerable influence to lobby on behalf of operators who are at the mercy of greedy developers that would be awesome however as successive ministers of both parties have let them get away with this gouging for so long now I doubt anything could be done now.
I don't feel any sympathy for the operators complaining about the 457 issue.