Wikel,
I believe what Superform meant was that if you behave the way 'locals' do (i.e. they are able to spend the time comparing prices from store to store) you would find the great deals. If you're really out for a bargain, get out them walking shoes.
I do not know about PD, but certainly in Cairns, there is heavy competition, and you find bargain chalk board deals. There is no guarentee on a reservation on the dive tour this way as this strategy is generally used by operators to fill up the numbers. They generally have a limited number of places on offer at these rates (much like the airline industry) and so internation tourists tend to guarentee their place by booking ahead since they are usually restricted as to how much time they have available and do not want to be disappointed. I would be highly disappointed if I dedicated 5 days to diving and couldnt go out because the dive boats were full.
For example, on my last dive trip, as an out of towner, I found a great deal, however, it did not fit in with my itinery (different companies launch on different days, so you MUST take that into consideration if you plan to do the el cheapo method). I found one operator with space at chalk board rates (the rest were sold out) and gave up some rain forest adventures to fit it into my schedule (I lost on a rainforest accomadation deposit but saved even more on the dive deal).
So really, locals = flexible. They're generally not restricted by time and are willing to sit out to get the cheapest deal possible (and those deals are GOLD!). If you book directly with the operator, you will most likely be paying RRP. If you book through an agent, they are almost guarenteed to be cheaper unless it's the Underwater Explorer (?) Research Vessel. Operators can give you the heads up with information that might prove valuable to you that agents do not know of (such as number of places available etc.).
What I ended up doing: Booked Chalk board deal in Cairns, booked through an agent. It was fantastic. Chalk board deals can not only be cheaper, but may even offer great rental deals. Perhaps even free rental to ALL gear if you're lucky, as was my case. The more flexible YOU are, the better your chance at getting a great deal.
Note: My trip was not a 1 day dive trip, so the conditions / restrictions I faced may not apply to you.
Good Luck.
