EWL,
Which agent res system are you using? I assume it's not Merlin direct - Galileo, Amadeus or Sabre? The last time I did the sums, the airline had to pay around A$17.50 for each return booking from one of these GDS, and that's before agent commissions and overrides.
It's good to see you back in the market; I hope you can understand why it took a little while.
Cheers