Your plan & itinerary are confusing to me. Nevertheless, my suggestion is as follows- If you are in Dubai, you can buy a bike there. It is 'relatively' cheap. You can then ship on Carnet to India since its closeby, sea shipping should be cheaper faster, while the carnet formalities are very easy (I shipped my BMW R1200GS on carnet from another country- Saudi Arabia to do a South India trip (had a blast with it!) and my clearing agent in Cochin seaport is an expert with Carnets and he especially handles loads of Hummers, Range Rovers etc on Carnet from Indians in Dubai). After your trip in India, you can ship it to south-east asia and later ship it back to Dubai. Once back in Dubai, officially sell it off to your brother in Australia from Dubai (export formalities in dubai are pretty straight forward & simple). Ship it off to your brother.
Forget about buying in India, not only is it complicated for a foreigner to buy, the custom duties being steep the approx prices at the official dealers in India would be as follows:
US$ 48,500 for a BMW R1200GS
US$ 22,000 for a Suzuki Bandit 1250
US$ 33,000 for a Yamaha R1 or Hyabusa