Anacortes Telescope supplies in the U.S. have the price of the 16" set at $1999US. that converts at .75centsAUS to about $2665AUD.
With some of the critical mods that were made to the 12" the extras on the 16" should be approx $80 for the new springs and (both sec & prim) collimation knobs. The only other needed extra is a shroud.
If you can handle the extra weight 60kg for the 16" and 35-40kg for the 12" you will receive as a bonus 77% more light.