I did these sums too and came to the same conclusion refer link
http://www.onlineopinion.com.au/view.asp?article=8569
At the time the $8000 subsidy was being offerred I emailed the PM (official site) and suggested that the net cost to the householder should be reduced to about $1000 and the subsidy increased (I also suggested a minimal system of 2.5 kw per installation was more practical)
I went on too quote stat's etc
Do you think I got a response, no way
This Govt struts around promising they will do something proactive but only if they can get the money out of honest joe citizen to pay for it