Australia has a pretty small domestic market compared to the USA. There's only about 9M people between the ages of 20 and 50 (just guessing that range is the Groupon audience). If you get 10% of that market, you've only got 900K users. This is pretty good, but nowhere near the scale of these sites in the USA. Even if you get every existing Australian in that age range to sign up, you're still not even half the size of Groupon.
An outcome like selling to Yahoo for $40M is probably the best possible outcome for an Australian Groupon clone. Unless my back of the imaginary envelope math is way off, I don't think the company could really objectively be "worth" more than that. Especially since Groupon clones are already a hyper-competitive space in Australia. Microsoft is backing a company, Cudo, that already has ads on network TV.