Black and white 4x5 isn't all that costly. A dollar-ish a sheet here in North America is very doable. Some films are significantly less costly than this. You will pay more in Australia due to shipping costs, but it shouldn't be horrifically more.
Colour film will cost proportionately more, but again I find it to be reasonable.
As for scanning, we have a sister site about hybrid photography (I don't do digital at all so I don't know the URL off the top of my head). This site concentrates exclusively on the silver process.