DAPs show you the sector entry for the approach you're doing which for me is a big plus. You don't really want to be playing with your hands and fingers in working out the sector entry when you're about to do an instrument approach (believe me, you'll be very busy!!)
Furthermore, if you're really short of cash, you can always access the latest DAP charts from Airservices Australia's website; print off the ones that you need for your training. All free of charge. (Although for flight test, I believe you need a set of DAPs to show the ATO that you have a current set of charts, AIPs and CAO's.)