This flight relies on a mismatch of first/business tickets to get you from Sri Lanka to Cairns, and return if needed.
Handy if returning from the sub continent in style.
To book, you'll likely need to price on matrix.itasoftware.com and use bookwithmatrix.com to book through Priceline. You could call the airline but as this may be an error fare, it's likely better to use the websites.
For more info: flyertalk
Colombo is one of the cheap ports to fly back to Australia. There are about 5 in the world that make for affordable business and first class. Cairo, Cape Town, Colombo, Istanbul and I think somewhere in South America also.