Apply for a private tax ruling from the ATO. There's a very good chance they'll declare you don't have to pay tax. There was someone on ausrace a few weeks ago who doesn't have a job so his sole income is from gambling. His turnover was about 3 mill/year but the ATO ruled he didn't have to pay tax. A private ruling covers you for 3 yrs then you reapply.
I think the ATO would be reluctant to declare your income as taxable because you could then deduct all your expenses and losses. They probably figure you just had a lucky yr and don't want to risk you making big deductions the next yr if you lose.