You answered your own question - people do it in AU for the same reason as elsewhere the $$$$$$.
Considering the difficulty in importing wild fish into AU, hybrid cichlids have become rather common over the past 25 years. Numerous crosses can & have been found in AU LFS, many marketed as something they are not. Sometimes there are nice stories attached, but when you dig deeper there is never any actual provenance to back up the stories.
Even here in NA, where trimac with real provenance back to the wild can be acquired relatively easily for those that are willing to source them, a boat load of hybrid flowerhorn crosses can be found being sold as either trimacs, or a flowerhorn of quality, to unsuspecting buyers. Flowerhorns that most serious FH keepers would flush, sold for $10, often far more, to folks new to the hobby. With hundreds of fry produced on a regular basis, even at $10 a pop the money adds up fast. Those looking for cheap trimacs, typically don't know the difference either, and genetics being what they are, sans some kind of provenance from a reliable breeder or importer, no telling what one is buying at your LFS, or backyard breeder. Hybrid trimacs were and still are a real problem in cichlid circles.