Unfortunately the income from landing fees and fuel does not cover the costs of providing ATC/AFS and general upkeep of runways/taxiways.
I can't think of an aerodrome where that income DOES cover the cost of providing those essentials, including, you may be suprised to hear, the world's busiest single-runway aerodrome down the road at Gatwick. Even LGW and LHR are dependent upon 'other' income to stop making a loss.
TheOddOne