There are two ways you can get paid to speak. The first is to be a paid keynote speaker on the speaking circuit. As a non-celebrity speaker in Australia you can expect to be paid $5k to $15k for speaking at a conference.  
 

The second way is what we call a 'busking out,' also known as selling from the stage. This is where you speak for free (or a nominal amount) but then sell something else at the end of the session.