One thing definitely worth a splurge of your trip money is a flight over Kakadu. All of the local people I encountered on my trip recommended it and they were absolutely right. Driving through Kakadu does little to give you the same perspective on the terrain, the interaction of the natural forces, and the sheer size of the park.
It is said that 10’s of thousands of years ago most of the Australian land mass was under water as a shallow sea- Kakadu included. The Escarpment is the menacing cliff face that basically denotes the edge of Kakadu and the beginning of Arnhem Land. It is believed that the gagged rock face was the shoreline during those times.
It is fine to hear those things, but it has far more impact to actually fly over them. From the air you can see the immense forces that must have been at work to so violently shape the rocks. Vast wetlands abrubtly end at cliff faces, massive rivers show the secret paths that they have cut over thousands of years, the intense loneliness of the aboriginal out-stations are witnessed, and of course you get to see several of the places Crocodile Dundee was filmed… 
The flight I took was $100 for 30 minutes. I went with the Scenic Flight Company. They are a small independent company that provides extremely friendly service. Their office is located behind the Mobile Gas station in town- not out at the Airport. Kakadu Air is located at the Airport and offers “Scenic Flights” please be aware. Kakadu Air offers a great gift shop and plenty of flight options, but they are a bit more expensive. Scenic Flight Company also offers internet access and lap top connections which are rare and difficult to come by in the Top End. Absolutely worth it.
