Thanks for your reply. I was trying to book using Stopover button on top of the page. When I used Multi-city Search I got a better price. Now there are 2 more questions:

What's the difference between Stopover and Muliti-city?
The price I got using:
Departing Brisbane on Thursday, 18 March, 2010
Leaving Iran on 14 April, 2010
Returning Saturday, 17 April, 2010 from Dubai

is $1970 not $1822. Do you know why?