The landing fee isn't for the tower, it's an Essendon airport landing fee. From memory, around $23 for 700 kg's. Not sure on other weights. The airservices (tower) fee is around $7. All up a nice little $30 bill in the mail a month later.
It's not necessarily just an en-route charge as you're mixing with Tullamarine traffic only a few miles away. Need an ATC buff to fill us in on more detail.